ArchiCad, EcoDesigner and Passive House

Project Energy Balance: a 5-second clip moving through 22 successive energy models where assembly details, windows, shading and systems are progressively optimized to flatten peak Summer solar gains to reduce cooling loads, while lowering heat-loss in Winter, and increasing Winter solar gains.

Any architect could design zero carbon buildings with a bit of help from a good set of tools. The economics of net zero energy design in architecture stands on its own. Saving the climate may be the imperative, but when the numbers are in our favour, what could possibly be holding us back? At this point it must be a matter of educating financiers, developers, architects but also the public. We can and we must design zero carbon architecture, but architects desperately need access to better tools, not only to support our designs, but to demonstrate the value of our designs to building owners and clients. To that end we have built our own apps such as our construction budget and performance calculator. This simple tool can set targets and establish values, but then we need serious design tools to the optimize performance of our architecture. For that we need to go much further with our BIM software tools to meet those performance and budget targets and that is where the BIM to BEM workflow that EcoDesigner comes into play.

While some of us architects have done energy modelling professionally for decades, we can’t all be energy nerds. At a certain point, the more experienced nerd-architect learns enough from the models that we tend to think we can skip the modelling and jump straight to best practices such as big overhangs or little shade fins to block Summer gains and receive Winter gains, selecting better windows, demanding verifiable air-tightness strategies and tweaking insulation levels. But even then, the same thing that worked last time can be improved on next time, and that is where having a simple, fast and easy energy modelling strategy in your back pocket can only help, not hurt.

The real promise of BIM/BEM (Building Information Modelling/Building Energy Modelling) is to get more and better information faster, directly from the process of creating architecture. This immediate performance feedback or what we sometimes call ‘design optimization’ or ‘performance optimization’ can lead to a streamlined coordination path, increasing the parity between the design model and reality, resulting in optimized results in the later stage BIM models. This latter part of a BIM/BEM workflow has been missing, or underutilized for decades.

EcoDesigner, used properly, is like having an energy-nerd on staff, available at any moment to test the impact of your design changes.

Dinner with the Graphisoft team in Budapest, 2006.

When Graphisoft introduced EcoDesigner back at ArchiCad 10 in 2006, I was thrilled to be invited to Budapest to join the Alpha/Beta testing team, and help influence the development roadmap. As a former R2000 program delivery agent, trained by NRC in Canada and having run thousands of Hot2000 simulations, I dove in deep and fast to witness the integrated BIM energy modeller firsthand. What I discovered was that the workflow, and the results were neither intuitive nor reliable based on parallel benchmarking with other established BEM softwares. I took a pass on working with EcoDesigner on professional projects at that time and didn’t give it much of a second thought, until now. With the release of ArchiCad 24 this Summer, I opened up EcoDesigner again with a new understanding of Passive House metrics. The European units and assumptions in EcoDesigner are now more familiar and with Passive House concepts making it to the international mainstream, getting other designers on the same page with respect to thermal design and evaluation conventions has never been easier. After nearly 100 simulation runs in EcoDesigner for AC24 in the past two weeks, either the software has improved, or my skills have, to the point that the results from ED24 now nearly match those from our other BEM platforms (PHPP/Hot2000/EnergyPro), some long-standing bugs and interpretive differences notwithstanding. The rest of this article gets a little technical but I’ll do my best to save you some time next time you try a simulation run in EcoDesigner.

1. Where do you start? Remember, Garbage-In, Garbage Out:

One can’t approach EcoDesigner with the idea that just any BIM model has the same capacity to be analysed thermally by EcoDesigner. Any BIM manager in a large office can tell you that every firm designs differently, and every user uses BIM software differently. We have all seen giant nightmare files with hundreds of layers, thousands of fills, hundreds of composites and even thousands of views, where it is a wonder that any meaningful collateral was generated from them at all. It sometimes appears that a room full of monkeys might have done a better job. That kind of model will not be a place to start. You practice will need to be at the top of its game in terms of creating a geometrically clean, orderly, and well-organized BIM file.

BIM users have different habits, hacks and workflows, and because of that far too many BIM models appear reflect a rush to meet various tender, permit or construction requirements, with little thought for comprehensive utilization of the ‘I’ in BIM – Information. Often early, and even late stage models are a hodge-podge of 2D and 3D information, corresponding to different issuance requirements, and rarely reflecting the clean totality of a watertight model designed to produce drawings, renderings, quantity-take-offs, thermal energy modelling and much more, but that is where we need to get to if EcoDesigner is going to be of any utility at all.

If we start with a well-developed template file, and a process and culture of BIM standards that results in a clean model, with proper intersection priorities, well-defined building materials and composites all neatly labelled and ordered, EcoDesigner simulations can be run in literally just a few minutes. The reason I am writing this blog however is to distill the basic information you will need to be productive in EcoDesigner without reading the 432-page manual, which by no means spells out every assumption for you. For example, how is Exterior Envelope Area calculated? This should be no mystery, but it is. Not understanding what is going on ‘under the hood’ can sow doubt and confusion among users. The very first thing a BEM manual should do is pair the results, with the methods used to obtain those results, and then help you understand how you need to model to arrive at the results you would expect. Reading the ED manual is a bit like a treasure hunt, with glints of gold every 50 pages or so but otherwise an incredibly boring read, and most busy professionals simply don’t have time for that. This blog is intended as a highly condensed, Quick Start manual of sorts. So let’s assume you have completed Step One – you have a well-organized template file and you have created a well-modelled building you wish to evaluate, proceed to step 2!

2. Create a Thermal View

You need to create a 3D view to establish the layer combination, dimensions and calculation units you wish for the Evaluation Report to generate. You also create a view so that you return to for your subsequent EcoDesigner simulation runs after making tweaks and improvements to test the performance implications of your modifications. This can be done right at the Schematic Design stage. You can even predefine a view called ‘Thermal Camera’ like we have in our template. This view should be set with a unique EcoDesigner layer combination that shows every relevant building component and nothing else. EcoDesigner does not care about your furniture, toilets, millwork, or extraneous 2D annotations. It does care about every wall, roof or slab that forms the thermal envelope of your building. EcoDesigner also considers your site or landscape mesh, trees, and other neighbouring buildings will all play a role in solar exposure analysis. Basically anything that casts a shadow in the 3D model matters – so make sure that stuff shows in your 3D view. Also, include your landscape mesh because ED will use it to calculate above and below grade heat flows, so make that is visible as well. Do not include interior glass partitions (ie. shower enclosures or glass stair partitions) as they will be included in solar analysis – so hide that stuff by layer.

Our thermal view is just as useful as a render view. This takes advantage of AC24’s direct Twinmotion link. EcoDesigner also considers the seasonal changes of deciduous trees for Winter solar gains – but we haven’t tested that yet.

3. Zones & Assemblies

The next step is to check that you have accurately modeled all of your interior zones. I can’t overemphasize this section enough, incorrectly modelled zones will result in entire floor or wall or window assemblies being excluded from your energy model – you need run a visual check (wireframe button on the upper left of the ED interface) to see that ED has captured every structure, and if not, you will need to review your model, staring with the zones. We use zones to model exterior and non-thermal spaces also, (like decks, balconies, breezeways and the like) so that we can include them in finish schedules. You will want to create or use a separate layer so you can hide any zones you do not want to be part of your thermal model view, such as zones you may use to schedule Gross Construction Area or Floor plate Areas.

PHPP pro tip: ED24 will use unconditioned zones to help you determine your Treated Floor Area or TFA.

Such spaces should include all ‘habitable’ rooms including closets, mechanical and storage rooms, stairwells and double-height spaces, but note that in PHPP you will need to omit some of these from your TFA which will penalize your overall EUI. Yes, closets are habitable. Have you ever been a teenager?

The TFA calculation method is unique to PH and no other BEM modelling workflow that we know of, so don’t consider this as a necessity unless you are aligning your design and modelling to arrive at an eventual PHPP output. Zones in a bedroom typically don’t extend into built-in closets if they are defined by walls, so we create tiny zones to fill closets, and just shut off the 2D stamps to keep our drawings tidy while maintaining an accurate count of all of our spaces.

Sidenote: we had a contractor charge us a significant extra to paint and tile inside 50 closets once because they were not noted in the finish schedule – never, ever again – account for every space, just exclude what is not relevant from your thermal model view).

IMPORTANT: You NEED to use the magical ‘Interior Wall’ method for placing zones in rooms or ED24 won’t work properly. That means, if you have a separate Kitchen and Dining room that share a spacial volume without walls, you will need to use a line with the checkbox, ‘Zone Boundary’ turned on. You should be able to select all zones on any given storey, and hit ‘Zone Update’ and get a positive checkbox beside every zone, this is a prerequisite for the next step.

However, if you hit ‘Update Zones’ from the 3D window, your zone updates will not respect those line boundaries because lines are not 3D things in ArchiCad. So we will recommend you only update all of your zones from the 2D/Plan windows, unless 100% of your zones are defined by walls as boundaries. Either way, you will almost always get a warning that zones are out of date. Ignore it, it’s a bug, I have never been able to get that warning to go away. If you know your zones are laterally and vertically accurate – you can review this in the 3D window by clicking on the little wireframe cube in the upper-left corner of the ED interface – you’re good to go.

Just a sketch of how ED calculates Exterior Envelope Areas differently from how a Morph Object derives these values. We did discover that modelling zones as ‘linked to stories’ gave us a more accurate interior volume on this building, where we have exposed floor joists and a 1.5″ structural decking as our finished floor and ceilings.

Zones are super important, it is how EcoDesigner generates the Key Values in the top section of your ED report like Gross Floor Area, Treated Floor Area, External Envelope Area, Ventilated Volume and Glazing Ratio – but don’t expect ED to give you PHPP-type results for these. Here is how ED calculates these things, to the best of my knowledge and based on firsthand experimentation and validation:

  1. Gross Floor Area: ED appears to uses the perimeter of the zones, plus the 2D/plan area of the bounding exterior walls, to generate a floor by floor count that sums into the GFA number. We have found this to be accurate to within 2% based on using a fill to calculate area to the exterior face of exterior wall assemblies. This difference may have to do with the volumes and areas of window insets, or column subtractions – all controllable in your calculation preferences in Archicad. We would say this is reliable.
  2. Treated Floor Area: As a user must assign Zones to Thermal Blocks, if interior zones are not mapped to a thermal block, they will not be treated as conditioned spaces, and therefore they will be included in the GFA, but excluded from the TFA. For PHPP purists, you will want to subtract stair-treads, and other non-habitable rooms (as defined by the German Wohnflachenverordnung), and the upper levels of double height spaces from your Thermal Blocks to arrive at a more accurate TFA for PHPP purposes. For the rest of us, assume every space is conditioned, unless it is not (ie. an attached garage or crawlspace). Also, reliable.
  3. External Envelope Area (EEA): So this one drives me a little nuts. ED starts its thermal calculations form the inside working out. That means what it calls External Envelope Area is the sum of all surfaces facing the exterior air, but from the interior dimension of the zones, not the exterior. Also, if you have used a mesh as your below-grade boundary as defined in the ‘Environment Settings‘ flyout menu, then these Below Grade wall and slab surfaces appear to be subtracted from the EEA. While this may be how walls are defined for fire-code analysis or limiting distance calculations, and apparently EcoDesigner analysis, it is not how Passive House considers exterior surfaces, which is instead like a bubble bounded by every surface losing or gaining energy to/from the environment, irrespective whether it is above or below grade, and it is measured to the outermost extent of the insulated envelope. Averaged above and below-grade surfaces are then treated separately in PHPP. We see the largest difference between PHPP and ED values with this value, where ED’s calculation of EEA in some instances is significantly less than that of the PHPP model for the same building. That said, ED is still calculating those below grade surfaces for thermal analysis, it is just using a different method to generate the summary EED value. If you need to determine an EEA for PHPP, you will want to create a Morph object and stretch its extents to obtain the desired EEA. EED calculation is therefore not reliable for anything other than ED’s purposes. (PHPP EEA calculation should be a feature request for a future ED version)
  4. Ventilated Volume: This one is pretty much what we’d expect. The total of all interior volumes as a summing of zone volumes, less interior walls and other elements that may get subtracted from zones (check your calculation preferences in ArchiCad). This is the same way PHPP considers Commercial Projects. In residential PHPP projects Vv is limited to 2.5m high zones, which for ED’s purposes, would not result in an accurate result if the floor:floor boundaries or connection to roof elements are discounted as a result. For the purpose of EcoDesigner calculations, you want your interior zones to be in contact with every bounding structure. A future feature of ED could calculate Vv differently for residential projects by simply multiplying GFA x 2.5m. For the purposes of ED simulations, and most other codes and standards, ED’s method for Vv calculation is reliable.
Helpful Hint: In the upper left hand corner of the ED interface you get a button that wireframes the 3D model data and gives you a coloured view of relevant zones, structures and openings. Use this to do a visual check that everything you want to see in your model got ‘captured’ by EcoDesigner. Try this in both ‘Tree View’ and ‘List View’ with the ‘Structures’ tab open. This is how you can scroll through all of your building assemblies to check for their inclusion in the thermal model. You can do the same thing for openings.

UPDATE (Aug 22, 2020): It turns out my basement slab was excluded from the PHPP export (thanks for noticing Ben Frost) which on review in EcoDesigner, was also missed, even though the zones in that lower level thermal block were properly constructed. This is because we model an expansion joint around slab edges, but because the slab was not connected to the wall faces, it was omitted from the zone calcs of ED. Again, check that all 3D exterior elements are accounted for. As you can see, ED maps areas of slabs and walls relative to your landscape/site/mesh, so model it carefully, as heat-loss to the ground is very different than heat-loss to the exterior air.

4. Location and Climate Data

You will need to properly set your Project North and Elevation, ideally from a surveyor’s drawing, and there are several ways to detail the exact project location and elevation above sea level. The simplest is just to pick the nearest city from ArchiCad’s Cities list, or add your own. This is only half of the climate picture however. ED24 will also want an accurate weather data file. You can use the default climate data downloaded from the Strusoft server but other users have found this to be inaccurate for solar analysis of windows. We prefer downloading the ASHRAE data automatically (it works sometimes) or manually, by pointing ED24 to a weather file. We find EPW format files work pretty well. Here is a few sources of climate files for Canadian ED users:


It must be noted that Heating Degree Days (HDD) and Cooling Degree Days (CDD) are consistently inflated by EcoDesigner by about 20-30%. We are not sure why it is doing this but it is a bug, and we have reported it and will be working with Graphisoft to update or otherwise fix this. This discrepancy appears to accounts for the 20-30% disparity we see between a test building modelled in ED and other softwares such as Hot2000 or EnergyPro, and we feel the results would be more accurate if this were remedied.

5. Thermal Blocks

This is a weird one. They should have just called this ‘Zone Groups’ because that is all they are, a group of zones that share an Operational Profile and Mechanical Systems. Once you have all of your zones defined, (we like to define them with numbers that match the storey they come from and colours to refer to the use type for easy sorting and assignment), you will then add your zones to one or more Thermal Blocks. Then you will tell that thermal block what Operational Profile you will be using. For a house, this will likely be the Residential Operational Profile. I like creating a Thermal Block for each storey of a building, especially because we sometimes condition upper floors or bedrooms differently than lower floors. For example, I may have a radiant hydronic system in a basement or lower level, but an upper mini-split system to allow bedrooms to have both heating and A/C in upper floor bedrooms only. Later you will assign your building’s heating and cooling systems to the Thermal Blocks , but you can run ED without them to generate baseline energy loads to determine equipment sizing. In that case, you will want all of your systems to show as ‘Not Yet Specified’.

6. Operation Profiles

Operation profiles are a combination of occupancy type (ie. Restaurant, Office, Residential) and user behaviour, and are likely defined in your specific region. In the USA these may be different than in Canada. They can also vary based on what modelling standard you are trying to match, R2000/EnerGuide will be different than PHPP. California (T24) may define profiles differently. For us, the (Canada National Building Code) required assumption for a house is 2 adults, 2 children, home 50% of the time. Each occupant has an internal gain contribution (140W/Capita), Service Hot Water load (I lowered mine to 50l/day to simulate DHWR, which is not available in the basic version of ED) and Humidity Load (5g/day/m2). It is unclear to me at this point in time what assumptions PHPP makes wrt user baselines as these do not appear to be spelled out in any transparent way in PHPP. Additional load profiles such as Lighting and plug loads are also defined in the profiles, they are kindof hidden away in the ‘Daily Schedules’ drop down menu, which looks like this:

So I can define a more granular Occupant load (ie. if nobody’s home from 9-5), Setpoint temperatures, Lighting Power Density or LPD, as well as plug-loads aka. Equipment Loads. If nobody’s home from 9-5, you don’t get the benefit of thermal gains in the Winter, but you also don’t bump up your cooling loads in the Summer. In any case, you should refer to your local codes to see what is the expected baseline for occupant load, and requirements for LPD, etc. Or you can just use the ED defaults for operational profiles, but just know, these may have a significant influence on your results. These are standardized for different energy codes because user behaviour and consumption profiles in Lagos, Nigeria will differ substantially from London, UK. We have used Office, Commercial Kitchen and Restaurant zones for a large restaurant project, and the estimated results are within the range of expected EUI values. You can reference these values from the OAA/SBEC/2030 table attached below:

7. Assemblies, Building Materials, Values and Structures

ED runs hourly analysis on every component in your building. It’s a good idea to have well-defined composites that in turn use well-defined Building Materials, refer back to Step 1 above! An airspace should be defined with the standard U values for airspaces. That said ED will apply its own exterior and interior R values, so they don’t need to be defined in your composites unless you have additional uninsulated interior chase/cavities and/or rainscreen cladding with an airspace. While EcoDesigner properly assesses the aggregate U-value of a series of different materials, it does not appear to account for the thermal bridging of framing members (we will be testing this later). For example, if you have Rockwool soft batts should be defined as having a U values from 0.035 to 0.04 W/M2K, don’t expect ED to calculate Effective U values for you by including the studies you may or may not model in the assembly. In other words, if you have a layer of studs and batts, where 10% of the composite is framing, then you need to manually calculate the effective R-value of that particular layer of the composite. That said, go ahead and run your simulation based on absolute or nominal R- or U-values of your insulated layers just to get a gross order of magnitude based on your building’s massing, orientation, and operational profiles and later on, when you really want to drill down and get real with the data, you can come back and calculate the effective U values of those layers with framing and you will see a small penalty in your total results, anywhere from 5 to 10%. What architects typically call assemblies, and what ArchiCad calls Composites, EcoDesigner calls Structures. You can review the structures that get included/excluded in the energy model later. For best results with your PHPP export, use the nominal values for insulated material layers in composites, and then do the framing-related effective value subtractions aka. vertical linear thermal bridges (as percentages) inside PHPP for each assembly type.

IMPORTANT: Do not use SEO commands to trim walls to roofs, or zones to roofs, as only TRIM commands will accurately modify zone volume and surface areas and the surface exposure areas of exterior walls, etc.

8. On Airtightness

Airtightness is best measured in the field with a blower door test. Values can range from almost completely airtight near zero, to leaky-as-a-barn at 5 or greater.

  • 5.0ACH@50Pa – Older or shoddy construction
  • 4.0 ACH@50Pa – Typical New Construction in NA
  • 2.0ACH@50Pa – Energy Efficient New Construction with consideration of airtightness detailing
  • 1.5ACH@50 Pa – R2000 Housing – A Canadian Federal Standard
  • 1.0ACH@50Pa – Extremely Tight Construction
  • 0.6ACH@50Pa – Passivhaus Requirement*
  • 0.0ACH@50Pa – Spacecraft

But as we haven’t built our building yet, we can only assume a level of airtightness. If you are aiming for Passive House levels, you will want your Air Change per Hour (ACH) or n50 number (for the PH folks) to show as 0.6 or better. Since ED does not let you enter a gross ACH test value (it would be nice if it did), you need to define the infiltration rate of every instance of your structures and windows. I prefer to zero out windows on an early stage model and apply an ACH value to walls and roofs. On a house with an ACH better than 0.6, enter something on the order of 0.1litres/m2 in the List View of the Structures tab of the EcoDesigner UI. We are only really interested in walls and roof values, you can zero interior walls. When all of my assemblies sum up, I get an ACH of 0.32@50Pa, which is better than Passive House but not so good as to be unbelievable. Your local building codes may only require an ACH of 2.5, but if you aim for that, you will be wasting a lot of energy unnecessarily. It is good to aim for a high level of airtightness, and find a builder with experience hitting these targets.

If you want to read more about the specifics on airtightness and Energy Codes, you can read more here:

Update: Our Passive House Canada PHPP instructor just advised us to enter a starting value of 0.6 for the n50 value. This is because one should not assume one can do better than this without field results. I take her point and will be updating our models to aim for 0.6 and not less.

9. Openings

Similarly, the stretched out List View for Openings will give you a ton of options. Most window companies have pretty good product data and testing sheets so you should be able to input values directly from these. For our test project, we have values for everything from air leakage rates as tested by CSA, to DST (Direct Solar Transmittance) to U values, so we have entered all of these respectively.

Pro-Tip: You can shift select and edit all similar assemblies at one fell swoop.

Here is what the list view of openings looks like with some real-world values:

If you don’t have ready access to window data, there is a somewhat hidden feature in ED where you can click on the three dots beside the Window Area heading, and you will get a super-detailed window picker tool where you can select glazing type, number of panes, airspace, gas fill, low-e coatings, frame types and all the rest. For PHPP wonks, you can even enter a linear psi value, which is a thermal bridge coefficient for frame edges. As a placeholder, psi values should be lower than 0.04 W/mK. However, don’t take a wild guess at this, as a good window detail is a mix of art and science. Use defaults if you have no idea how to draw a good thermal window detail. ED STAR can help you determine this value with its graphical thermal bridge tool, which is also available in regular ED as a trial, but sadly the trial version won’t give you the psi values, just the pretty coloured thermal flux layers. This is one of the key reasons we’d love to see a return of the STAR version to international markets.

This is pretty much the goal. We have a large balcony above this window that is designed to fully shade it in most of the cooling season, but let 100% of the solar gains inside in the heating season to optimize performance. You can literally ‘see’ the shape of the balcony from the window’s perspective, represented by the light blue ovoid over the yellow wave. UNTIL you perform the calculation, nothing will show here. If you have a slower machine or older hardware, go get a coffee and come back later.

Solar Analysis is one of the coolest features of ED. It creates a shadow and gain map of every window of the building, for every hour of the year, based on the weather file you have selected. You will want to be sure your weather file is a good one, and an Ideal Year is a best average, whereas an actual year may have some outlier data, for example it might have been super cloudy in 2018. Once you run this hourly analysis, your solar gains calculations for all seasons will be much more accurate. What you want is high gains in the heating seasons and low gains in the cooling seasons. ED uses any element that casts a shadow over the windows such as slabs, columns, trees, neighbouring buildings, shading fin library objects to create this map. However, those elements must be visible in the 3D view you created, what we call our Thermal Camera. I have an iMac Pro with 10 cores, and this calculation takes about 5 minutes and my fans spin up, so you know this is one of the few times you will be exercising your machine to the max. The results are pretty awesome and useful, in terms of tweaking shading elements for optimal energy performance. If you are getting nothing but dark blobs – you may have a lousy weather file. Check that first before going on a rant about how ED is inaccurate – again, GIGO is key here.

NOTE: there is a provision to manually enter ‘virtual’ overhangs and side fins etc. on a per window basis right inside ED, but I will be switching all of these off now as I see how shading masks are calculated by physical, shadow-casting objects in AC, making the ‘virtual’ shading redundant and probably less accurate.

10. Systems

I’m going to expand on this section at a later date. Suffice it to say that the basic version of ED gives you a limited palette of options for systems, but it should be good enough for most architects to perform energy evaluations with, in order to progressively refine and improve the passive or architectural elements of the thermal design.

Some helpful hints: If you are using an Air:Air Heat Pump, choose a ‘Water Heat Pump’ and set the Source to Air. Also, you may want to check your Service Hot Water Heating settings and set the high temperature to 49ºC (which is our building code max. to prevent scalding). This will have a pronounced effect on your DHW loads.

If you are using an HRV in an Airtight building, you may only want to define the Heat Recovery Ventilation system by type ‘Supply and Exhaust’ and set a constant airflow volume as required. Passive House uses a Volume method to determine this which is 0.39 multiplied by the Ventilated Volume, which in our case gives 147m3/hr – a good placeholder for early modelling, and you will place that rate in the Operation Schedule of the HRV dialogue.

We use metric units for almost everything to do with an energy model in Canada. If you are in the USA, you can change units to Imperial R values and kBtuh, etc. as desired. This is based on Working Units, Calculation Units, and a few settings in ED. Finding every location where you can edit units is a bit like an easter-egg hunt, which is why I am not explaining here how to catch them all. If you can’t get the results you are after, fee free to PM me. There are a few tips and tricks to get the exact units you wish for any given input parameter or reporting units – just knowing that should help you find them on your own.

Your primary energy mix can be accurately calculated from this dialogue, which for Ontario is as above.

11. Thermal Bridge Analysis

In the non-STAR version of EcoDesigner all you can do is ‘Try’ the Thermal Bridge analysis. So I did. You need create a detail, open the detail, convert any of the drafting or cut fills to ‘Building Material Fills’ – use Find & Select to kill all of the ‘Empty Fills’ or otherwise non-thermal fills and then invoke the command from the Design/Energy Evaluation/Thermal Bridge Simulation. Invoking the command from the detail view-map by right-clicking ‘Thermal Bridge Simulation’ will fail. Step through the process and you can then hit ‘Start Simulation’ and you’ll get a window that looks like this:

I set my Exterior Temperature to -10ºC and Interior to 20ºC. While you can see there is a Psi-value cell, it is greyed out because that is for EcoDesigner STAR users only. This is possibly one of the most useful features for calculating linear thermal bridges for PHPP compliance purposes (it remains to be seen if PHI would accept ED bridge simulations on par with Therm, Flixo or other apps), and is SUPER EASY to run – if only we could see the results! One remaining question I have is do I need to create a special ‘Triple Glass’ material so that I can add that fill, with the correct centre-of glass U-Value to my assembly to generate an accurate result? We can only know with the STAR version of EcoDesigner, but this is clearly easier than using Therm or any of the other TB analysis engines out there. Until the STAR version of ED is available again, we’ll all just have to wait.

12. The EcoDesigner Report, and Building Code Compliance Documentation

Here is the definition of what we need to provide for permit compliance in Ontario, Canada (OBC-SB12):

The key word is “may be used“. On clarification from the Ministry governing the OBC here, I received the following response:

If you look at the appendix A- it says that …”the following software may be used:…” meaning that they may be used, not mandatory be used. Please bear in mind that the purpose of the Appendix is to help users to understand the particular Article and appendix is not mandatory. Again, as I mentioned in my previous email, it is up to the building official to decide about the acceptance as he or she is the authority having jurisdiction. There is always option for the Building Code Commission tribunal to determine the compliances with the Code in the case of dispute between the applicant and the building official. Regarding to your question about the possibility to re-phrase the contest, that require procedure and certain steps shall be followed. The first step is to submit the Code Change Proposal that may come from anybody.
Building Code Advisor, Mechanical Specialist
Ministry of Municipal Affairs and Housing
Building and Development Branch

Some markup to help make sense of the EcoDesigner Report Chapters. This sample file is Passive House aspiring, but we are far from reaching that goal as you can see from our Building Shell Average U-value and PER values, but successive iterations and design improvements will get us there eventually.

I plan to submit a request to our governing code authorities to either add EcoDesigner and other tools such as, or provide clarification in the code that the list of acceptable softwares is not exclusive.

So after all, the final goal of doing all of the work to understand and validate this BIM to BEM workflow, beyond performance optimization, is to generate some useful collateral, such as the Evaluation reports, which we plan to submit for code compliance. That is what we have done here. And yes, this was not done blindly, we have validated these results against other BEM platforms. If anything, EcoDesigner is more conservative than the other platforms we have tested against by at least 30%. We feel this corresponds to the roughly 30% EcoDesigner is inflating our HDD by, as noted above.

We will be submitting two carefully formatted EcoDesigner reports, using RSI values for thermal resistance (instead of U values, as that is what our local AHJs will expect), and referencing a baseline model using R values from a prescriptive path submission, to demonstrate we are in fact using less total energy than the reference model. Since regular EcoDesigner (not STAR) does not automatically create a reference model analysis, we need to create the second model with R-values that match the code minimum. This is double the work but that’s why we feel the re-release of EcoDesigner STAR is so important for architects. Attached is a DRAFT copy of a completed ED simulation report below that you can download. Please add any comments or questions in the comments field below and we’ll be sure to answer them as soon as possible!

13. PHPP Export

On the EcoDesigner interface, there is a little triangle at the lower right, with a flyout window that offers several export options, including gbXML, VIP-Energy, ‘Save as Baseline Building’ and finally PHPP. You will need to be running a legit copy of Microsoft Excel with a licensed copy of the PHPP workbook. When you select the PHPP export option, it prompts you for your PHPP workbook, which you point ED to and then presto, ED fills out some of the tabs in the PHPP workbook, notably the U-values and Areas tabs, together with all of your doors and windows. That said, some of the expected Key Values like location, climate, project name and address, etc. are not passed from ArchiCad to ED to PHPP. It looks like there is some room for improvements in this regard, because if the ED model is developed with an eye for PH validation, then there is far more data that can be mapped between the platforms. Here are the tabs ED does write to in PHPP:

  1. Areas
  2. U-Values
  3. Windows
  4. Shading (to be confirmed)
  5. Annual Heating
  6. Heating
  7. Heating Load
  8. Summer
  9. Cooling

There are dozens of parameters that could be transferred from ED to PHPP but are not, which suggests Graphisoft and PHI should meet again to update this mapping process for a more complete picture of the assemblies, as this is a huge timesaver – when it can be relied upon. As a quick check, one can review the Key Values of the EcoDesigner report and search for offending U-values. We saw that the upper range of our windows were out of spec, and then noticed we had updated some zones with a new category and that had reset the windows that were previously defined in EcoDesigner – window parameters to not belong to the ArchiCad window object, but rather they are defined in EcoDesigner separately. It is uncertain whether EcoDesigner will calculate effective U-values by accounting for framing in the insulated layers, but we will trial this next. It really should because no composite assembly is a pure cake-layer of insulation, and Passive House expects a proper reckoning of all linear thermal bridges, vertical ones as a percentage in component take-off sheets and horizontal ones in the junctions section of PHPP. Other offending U-values can be the linear thermal bridge created by interior wall to exterior wall junctions. While these show in your ED report in the Key Values section, they are not seriously detrimental to your energy performance or your PHPP export results.

We feel strongly that is the only truly international energy modelling standard that has been adopted worldwide by architects, improving PHPP export from EcoDesigner to a level even exceeding Sketchup’s PHI-developed DesignPH, should be a goal for Graphisoft.

On Ashrae 90.1, Ashrae-140, 2007 Compliance

We recently received a response from ASHRAE around compliance with ASHRAE 140:

There is no such thing as ASHRAE 140 certification. The process you described is what certification would be except that 140 does not (yet) specify ranges of acceptable results or other acceptance criteria. We are in the early stages of that process. What you see here ( is a list of software that submitted 140 results and by that dint alone (maybe one or two other small dints) are deemed acceptable for the 179d tax credit. Many other programs simply reference this list. There is no fee associated with either the submission or the listing.

from an informal email with ASHRAE

Some Notes & Questions:

  1. ED Successfully captures location data (Lat/Long/Elevation) from the site data added to AC
  2. Climate Data Source: This says ‘StruSoft Server. All data should come from the Canadian Database for past and future weather at: – This gives current year Heating and Cooling Degree days (CSV file attached) in both a JSON or CSV exportable format. This is a federal site created by Environment Canada and the University of Montreal. 
  3. Building Geometry Summary is 100% correct based on standard interior room zones grouped into thermal blocks, but questions remain around how Exterior Envelope Area currently is and should be calculated.
  4. Glazing Ratio is not calculated based on Window:Wall Ratio or simply WWR, but as a percentage of above-grade envelope surfaces which includes your roofs and slabs exposed to exterior air, somewhat similar to how PH considers this percentage with the exception of ED excluding below grade surfaces from the Glazing Ratio.
  5. Specific Annual Values: Net Heating Energy: in our lingo this should be called TEDI or Thermal Energy Demand Intensity.
  6. Total Net Energy: This should be called TEUI or Total Energy Use Intensity – this is a North America wide term, but units in Canada are the same as ED defaults when metric working units are selected for calculations insider ArchiCad: kWh/m2/a. I suspect if I want the correct units to display I need to set both my working units and calculation units in ArchiCad preferences, and in the units tab at the chapter headings right in the EcoDesigner report screen. Primary Energy is calculated separately from Total Net Energy. Primary Energy is calculated according to DINV-18599
  7. Energy Consumption: I don’t understand how this is different than Total Net Energy, is it energy less the source geothermal contribution ie. ‘External Air’? If so why is it always higher than my Total Net Energy?
  8. What determines the report’s ‘Energy Consumption by Targets’? Don’t I need a reference model for that? (STAR only)
  9. CO2 Emission: Current lingo here is GHGI or Greenhouse Gas Intensity – units are correct at kg/m2a, and the suggested units are believable given the Ontario Hydro energy supply, which we have input. 
  10. Degree Days: This is a fatal flaw. This results in too high total consumption. ED assumes 7126.6 HDD, when in fact the heating degree days for Utterson, Ontario is only 3718.13 – this is the only thing that is throwing the data off completely!! Pulling data from ASHRAE/IWEC/TMY/WTEC2 files had no effect at lowering these erroneous values.

Thanks for taking the time to read this summary and I hope you find EcoDesigner as useful as I have. If you have any questions feel free to comment below and I will do my best to answer them! A.



  1. Architects as Energy Experts – thomson | architecture inc. left a comment on September 10, 2020 at 5:03 pm

    […] ArchiCad, EcoDesigner: I have written extensively about EcoDesigner, the first and only truly integrated BIM/BEM modeller we know of, it runs hourly analysis directly inside of ArchiCad using AC’s native Zone tool, and is super fast. Features include graphical thermal bridge analysis and hourly solar mask calculations for every opening. This takes some considerable ArchiCad knowledge to set up and run correctly, but the results are amazing and allows customized report exports, detailed spreadsheet and gbXML export as well as partial PHPP export. Ease of Use: Moderate […]

  2. D021 left a comment on October 1, 2020 at 7:19 pm

    […] Ez a BIM to BEM: épületinformációs modellből így lesz analitikus épületenergetikai modell, legalábbis nagy vonalakban. Lépésenként haladva előjönnek a kérdések, egy olyan ember számára is, aki ért hozzá, nem csak bohóckodik. […]

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