Choosing an architect for a low energy (passive?) new build

[WisteriaMews]

We built our first house back in 2015/6 and are lucky enough to be in a position to do it all over again. We're currently choosing between architects.

We're aiming for a four bedroom low energy home. Getting Passive House certification isn't a requirement, but we'd like to be approaching that level.

We are considering using the architect that we used last time as we know we have a good working relationship with them, they are local and they have experience getting challenging planning permission applications granted (we have a tricky sight). On the downside they have very limited experience with Passive Houses. They are currently designing one for another client. As they don't currently have anyone qualified in the office, they are using a consulting firm for advice, PHPP modelling etc.. None of the contractors they work with have built a Passive House before.

One of the other architects we're speaking to has been Passive House certified since 2010. They have done multiple new build and retrofit Passive Houses. Clearly they know how to reach Passive House standard and have relationships with timber frame companies and contractors who have achieved it in the past too. On the downside we don't know how well we'd work with them (I'd rate the relationship with your architect as the most important one of the whole process as it can be a 3yr journey together) and they are based a bit further away so have less local planning knowledge and would be less convenient for meetings etc...

 

Would welcome the thoughts of those that have successfully built a low energy / Passive House before. How critical is the architect you choose? It is essential or as long as you get the PHPP modelling done and get a Passive House consultant it doesn't really matter?
 

[JohnMo]

I would rather work with, with being the important word, an architect I have a good relationship with.

 

Teach yourself about thermal bridging, insulation continuity etc, same for airtightness principles.  Formally review the architect drawings to ensure you have what you want, get him to change what's required.  Be an active client, explain this to the architect from the outset, as most client are passive.  Nothing is approved until it's approved by you.  That's how I did my design.  It may not suit you, if that's the case go to the architect you don't know, but with passivhaus design experience.

 

Remember - Form factor is important, basically the closer the building is to cube the more efficient the insulation becomes.  Our house is as far from a cube as you can get, if we insulated a cube to the same standard as we have, it would need no heating.  But a cube building on our site would be wrong and look out of place.  So we have heating.

[JohnMo]

Forgot mention, we had no PHPP modelling done or any consultants. 

 

Most building firms don't have a clue about airtightness or low energy building, nor most plumbers for heating system design.

[Gone West]

7 hours ago, WisteriaMews said:

Would welcome the thoughts of those that have successfully built a low energy / Passive House before.

We designed and built our own house to PH standards and didn't use an architect and I did the PHPP modelling. We were members of the AECB at the time and spoke to local architects about the build and had large numbers of AECB members visiting our site. From what we found out, there was little understanding of what PH really meant and the only certified PH architect visitor didn't fill me with confidence. I must add this was twelve years ago and things may have improved. I certainly wouldn't bother with employing an architect unless they were PH certified. It's important to model the design using the PHPP as you are then able to vary different aspects of the construction to find out where changes can be made to improve overall performance. By using this method we were able to build the house without having a conventional heating system and to design the internal layout to suit our requirements.

 

[bgmill]

If we started over I would definitely choose an architect that has proven experience/accreditation in PH design. Ours spoke a good game and convinced us that they had the skillset but it quickly became clear that they had little ability or desire to go beyond basic building regs requirements in terms of thermal performance. Not a single mention of PHPP modelling and they wanted to draft in a specialist when I queried some quite obvious cold bridges in their designs (at my expense).

 

All told, I've had to take a far more active role than I had wanted to - constantly reviewing their work, challenging poor decisions and researching alternatives - which has eaten up huge amounts of my time.

[joe90]

I didn’t use an architect but had a great builder who understood Passive house principles, I was very involved in the build being on site most of the time. I would say the relationship with whoever (architect or builder) is important.

[Bitpipe]

When our house was designed back in 2015 neither we or the architect had any appreciation of low energy or passive build principles - main objective was to get PP.

 

We had a 18 month hiatus between getting planning and detailed design drawings during which we discovered this site's predecessor. When we were able to move forward, we did so armed with a lot of knowledge and the decision to PM ourselves and use a passive timber frame firm for the build (MBC). We did hire a consultant for a few months to do PHPP and draw up a cost model but did not feel that they were value for money thereafter.

 

Architect had limited input post planning as they would have been recycling the MBC detailed drawings and charging us significantly for such.

 

I believe that the build contractor is the critical element as unless they are comfortable with low energy builds and experienced, all of the effort expended ahead of that could be compromised through poor implementation and attention to detail (especially airtightness etc). They will refine architect details and if brought into the process early enough can probably help see off any particularly bad decisions.

 

I would suggest you use the architect you like but make sure that they understand how their 'big' design decisions impact the energy performance  - especially solar gain - and then either get them to do the PHPP modelling directly or through a contractor or consultant.

 

I'd suggest that pretty much any building design can be made to meet passive standards unless there are some design choices, i.e. acres of south facing glass etc that would make it particularly challenging. 

 

 

[joth]

On 21/08/2022 at 08:35, WisteriaMews said:

None of the contractors they work with have built a Passive House before

Some questions to ask your architect:

How important is it they use one of their regular contractors?

Would they be open to a different build method such as timber frame with off-site construction that comes with a guaranteed airtightness like MBC?

Will they be contract administrator to a main contractor?

Are they happy to write airtightness requirements into the contract, and hold the main contractor to them? (even when they try a wriggle out claiming airtightness was impossible due to a specification error from the designer)

 

As others mention if you know you have a good working relationship with an architect I'd be tempted to go with them, but these are some more questions that will help ensure the build itself can meet your goals too.

 

 

 

[Thorfun]

I think that you're favoured architect you have a good working relationship with using an external consultancy for the Passive House work is actually a good thing! I'd much rather a professional admit when they don't know something and get someone in that does than try and muddle through and wing it.

 

knowing your limitations and when to ask for help is a great trait and I applaud the architects for taking that approach.

[SteamyTea]

When designing anything, the big decisions have to be made first.

So in the case of a house, decide how much energy you want it to use, and when it is used.  This is where Net Zero becomes a bit confusing, a lot of houses can be energy neutral, but you may still be importing 10 MWh in the winter, while exporting 15 MWh during the rest of the year.

Be careful how you measure the energy usage, a kWh.m^-2.year^-1 metric does not actually tell you a lot. Much better to say 'I want it to use no more than 1 MWh for heating in a year.

That then opens the next question as to where that is primary energy or delivered energy.  This is where the technology starts to come into play.  Different technologies have very different efficiencies: don't believe the manufacturers claims.

CO₂ emissions are also important, to keep them low you only have one choice, electrification.  Generation is getting cleaner every year.  If that is the route chosen, then PV is a must.  This will set your roof design and house orientation (to the sun).  Ideally you want to have no shading and possible multiple angles to spread the power delivery throughout the day and the seasons.

So now you know how the roof will look, and how the house is located on your plot, the details can start.

Those details may include location of waste treatment plants, water boreholes, connection to existing services, road access and parking, views and landscaping.

Get a feel for that, and you are now into more details such as room layouts and location.  Too may people start with the internal layout and hope it fits their plot.  Seen a bungalow near me that has a lovely floor to roof sliding door, the view is a stone wall, less than 3 meters away.  Then they put the garage in front of the kitchen window, but left enough view so that passing car's headlights shine into the bedroom.  Was on the market for years; I assume they sold it to a blind person.

 

When it comes to building a low energy energy home, it is all down to detail, both architectural and engineering.  In reality, architects are just trying to hide good engineering details.  There is no myths in what is needed to create a house to passive standards, anyone could do it with a spreadsheet and a book of material properties.  The architects job is to make a properly sized widow and door fit into a 300mm thick wall.  If the only way to control solar gain is to add blinds and shades, the initial engineering has gone wrong.  Review it.  Good engineering practice is what makes a low energy home, not bolt on afterthoughts that are only useful for 15 days a year.

And don't get stuck on building materials, there is nothing wrong with a combination of masonry, timber and steel.  They just have to be interfaced correctly.

 

So, get a good structural engineer, a good understanding of building physics and a builder that you can trust and is willing to learn or at least does as they are told, then get the architect to make it look acceptable.

Too often it is done the other way around.

Edited August 23, 2022 by SteamyTea