HPH310 : Important takeaways from an exemplar straw panel Passivhaus
Juraj Mikurcik, Nick Grant and Mike Whitfield reflect on the award-winning Old Holloway project, which is built with EcoCocon straw panels and is a certified Passivhaus.
This podcast is slightly different to normal because it's been compiled from video footage. The video, which can be seen above, is a 10-minute overview of Old Holloway (or you can watch a 2-minute version here).
Passivhaus specialist Nick Grant and Passivhaus builder Mike Whitfield have both been on the podcast before. Architect Juraj Mikurcik has been a friend of House Planning Help over the years and we were delighted to see his home win at the UK Passivhaus Awards and highly commended at the ASBP Awards.
This podcast explores what makes this house build so special.
The design decisions are easy to read and appreciate
In an era of climate emergency we should all be thinking about limiting our environmental impact and reducing our energy consumption.
Old Holloway (with a floor area of 95m2) was built to a tight £150k budget and achieves so much. Not only is it a highly efficient home, but it's been built with as many plant-based and non processed materials as possible.
Constraints impacted the form of the house
The project faced tough planning challenges to get a building consent, needing design approval from the Duchy of Cornwall estate (who sold Juraj the land) before even submitting an application to the local authority. These constraints led to a single storey building and perhaps the rural aesthetic.
Nick Grant says it's his favourite house for all sorts of reasons. Mike Whitfield feels the atmosphere in it or soul quality is really good.
Sufficiency and affordability informed the scale
When it comes to scale it's about finding the right balance. If you build too big you have redundant space whereas if you build too small then people struggle to go about living their everyday lives.
Juraj compares Old Holloway to the TARDIS, because it looks small from the outside but feels big from the inside. An open cathedral ceiling helps create a great sense of space.
Nick also believes small buildings have an advantage.
“Small buildings can look interesting because the texture and contrast of the materials is enough. When buildings become very big that's not enough. So however characterful the render is or the brick, it still looks big and bland, so you then start articulating the building and adding bits on because you think it looks plain.”
Re-evaluating how much space you need is a smart move… but it's also important to build what you can afford.
Materials matter when building a Passivhaus
If you care about the environment then reducing the embodied energy of the building is essential.
Mike says that some people believe it's either natural materials or energy efficiency.
“You can construct an argument to say that the embodied energy in a Passivhaus isn't that important because you're going to save so much energy over the life of the house.”
This might for example lead you to build with insulated concrete formwork.
Juraj specified a Passivhaus certified straw panel system.
“Ecococon gives you a really instant, pre-fabricated system that is genuinely low energy.”
The structural concrete slab is also the finished floor
At the base of the house a concrete slab has been used, but this structural slab doubles as the finished floor. It took Juraj an incredible 90 hours to polish it!
This route is cost effective. The only downside is that it's tricky to guarantee a certain finish.
The straw panels are wrapped with an airtightness membrane
Nick's house was built with straw bales and he often dissuades people from bale building because it's hard to get them to perform well.
Juraj stresses that EcoCocon is a timber panel based system, produced in a workshop, that uses compressed straw as the infill insulation. As such it's even a Passivhaus certified component.
To achieve Passivhaus airtightness requirements the building is wrapped with a membrane on the outside. Nick explains that generally having the airtightness layer on the outside is something they try to avoid. Juraj has been careful to specify the right product in order to avoid condensation issues. The membrane has vapour openess and the whole build was modelled in WUFI.
Don't be afraid to experiment and seek advice from others
Old Holloway is clad in charred timber. This is something Juraj had been wanting to experiment with for some time. He loves the finished effect it created, even if the process was time-consuming.
Juraj believes the crinkly tin roof is the biggest bargain of the whole project. He calls it a ‘very Australian detail'.
Nick says that it's good to see it used simply.
Woodburners/stoves are not a great fit for Passivhaus
One thing Juraj would do differently is not include a woodburner. Although it can be incorporated in a Passivhaus (and has been here) there are lots of reasons to deter you.
- There are better ways of providing the background heat.
- It's old-fashioned thinking (burning anything releases a lot of particulate which is not good for health). People like Passivhaus because of the indoor air quality but having a logburner – no matter how sealed the system is – does release particulate into the room (which appears on the MVHR filters)
- It is a faff to clean up
- It takes up space
- You have to keep children away from it
- Even though it's sized correctly, it is not the same experience as a roaring open fire in an in-efficient house. Nick comments that on social occasions the fire is always out before he arrives because the house is already warm enough!
Nick, Mike and Juraj all have fires, but now say they wouldn't do it again.
Mike suggests that if somebody is fixated on having a fire, then go for a bioethanol burner. This can give the effect of a fire but doesn't need lots of kit. And if you decide it's a waste of space you can just get rid of it!
Total control over solar gains in summer is a masterstroke
Sensible glazing ratios, a significant roof overhang and a pop-up awning make Juraj's house one which will not overheat.
The Passivhaus process is always looking for the best form factor. Old Holloway is not an exact rectangle because it dips in on one edge. This hasn't been done because the shape looked boring and it needed to be articulated: this provides complete solar shading of the biggest windows in summer and a nice area to sit outside whatever the weather.
“You go from a box it's more expensive, so then you've got to say is it giving me some value for money, and here I think it really does.”
Find out more
Visit the website of Old Holloway
Visit the website of Mike Whitfield Construction
Visit Nick's website for Elemental Solutions
Follow Juraj Mikurcik on Twitter
Follow on Nick Grant on Twitter
Download a PDF transcript of this episode
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