There are plenty of spruikers for residential Passive House (PH), but what about all those leaky B and C grade office buildings that are past their use-by date and yet have too much embodied carbon to lose in a knockdown?
They’re perfect for a PH retrofit, according to Julian Sutherland, who will reveal how at our Big Debate on this curiously contentious way of building, next Tuesday.
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You can apply PH without too much effort and give these old commercial buildings a new lease on life, he says.
Sutherland is an engineer and head of sustainable assets with JLL, formerly with ARUP and Cundall.
He’s also a member of the Passive House Institute and has built his own PH in the UK. He’s used the system for a 2400-person school in the UK as well as a 350 unit residential development above a shopping centre – and his own retrofitted home.
In other words, he’s well on the keen, “yes” side of this debate.
“The only system that I’ve found in 35 years of building engineering and physics that actually gives you the low energy solution is Passive House. I’ve modelled things to TM 52 (energy modelling system). I’ve done all sorts, I’ve used building codes from, I don’t know, a dozen countries around the world, none of them deliver that outcome.”
Most of the discussions around PH focus on residential buildings, but Sutherland says there’s a big missed opportunity for commercial buildings.
These are the many old buildings where you start with the window upgrades because so many are “old, leaky, single glazed” and thermally broken.
If there’s a spandrel, that could be a bit of a challenge.
But even so, you can insulate the spandrels either from the outside or the inside.
“If you can do it on the outside, it’s better. Then you can put new windows in, so suddenly you’ve fully insulated floor to floor on that basis, and you can just keep on going.”
You’ll also need to basically reskin the building with a weatherproof membrane, a gap to allow the rain to permeate through, and to which you can attach an aluminium panel or fibre light panel, “or even a piece of glass”.
The cost might be $20 million for a 20 or 30 storey building but the alternative is “you’re stuck with a building that is basically in very poor condition. It’s very uncomfortable, leaks like a sieve, and is probably not delivering the performance that a new tenant wants.
“You’ve got to electrify, and you’ve got to reduce the energy of it. So the only way to do that, only way to change that, is you have to reskin it, and that’s this whole retrofit piece, where you basically strip it back to frame, then re-engineer it, externally.”
Sutherland says the owner might also investigate adding some additional floor areas on the roof or reclaiming an atrium to add lettable area. All adding value.
“You’re basically taking an old B, C or D grade asset and turning it into a prime asset.”
“The business case comes with it, because you’re getting more area to sell, your rent’s up, your vacancies are low, you can borrow the money cheaper because it’s sustainable, and all those things come together.
The method can be applied to schools, hospitals, local authorities and high-rise buildings, Sutherland adds.
“There’s one in the middle of New York that’s a certified Passive House – every single building type you can imagine, there’s a Passive House version of it, and there’s lots of it.”
In the UK these discussions about Passive House happened ten years ago.
Sutherland has built his own PH – a retrofit in the UK – a 2400-person school all in cross laminated timber, “basically net zero carbon” and his team was delivering the standard across multi residential high rise of 300 and 400 units.
And that includes social housing.
“Because if you want to manage your risks in a social housing environment and you want comfort… and avoid mould. The only way councils could manage that risk was to go Passive House.”