How to build your own Passivhaus in 231 easy lessons

Ben in front of house
CC BY 2.0 Ben Adam-Smith in front of house/ Lloyd Alter

Ben Adam-Smith of House Planning Help shows how it's done.

Ben Adam-Smith has been promoting good green building in the UK for a few years, teaching people how to "self-build" or do their own project, which can be very complex anywhere but more so in the UK where there are many zoning and greenbelt restrictions. He produces a great podcast at House Planning Help that I have been on twice (so you only have to listen to 229 lessons), and have followed his search for his property, his designing of a Passivhaus, and ultimately, it's near-completion.

While in the UK for a few days I took the train out to Welwyn New Town to have a look at this house with such an interesting history.

House in filedHouse is hidden behind other house/ Lloyd Alter/CC BY 2.0

It also has a really interesting geography; Ben had found a lot that was mostly unbuildable because it was on the greenbelt, where development is extremely difficult. There was a small portion of the property, behind another property, that was actually buildable; only someone interested in building a small house, and being essentially invisible from the street, would be interested in this property. That's one of the features of the house that makes it so attractive; the great bulk of the property is now available for landscaping, gardening and kids playing.

Spot the house from the streetSpot the house from the street! / Lloyd Alter/CC BY 2.0

It is so invisible that the internet technician couldn't find it, which if Ben was in any other business than video blogging would be a feature, not a bug. The restrictions on the lot ensured that this is very modest compared to its posh village neighbours with their Porsches and Land Rovers.

The house is low key and understated, finished in lime render on block. It's architecturally modest to fit in with its neighbours but technically sophisticated. I've rarely seen a house that was so deferential to its neighbours; there are almost no windows facing them and those that are there are obscured glass, and the roof has a crick in it to reduce the slope that might make the roof too tall and visible. Ben and his architects, Parsons + Whittley, have done a terrific job of discreetly fitting in.

Installing block foundation© Ben Adam-Smith

There are a number of features that seem odd to my North American eye; I had never heard of the beam and block floor system, where precast concrete slabs are dropped into a grid of precast concrete joists set a foot above the excavation. On the blog, Ben explains:

At the start of the millennium, solid concrete slabs were still the preferred method for ground floors in most houses. Today, things are different, and most are built in the beam and block style...There are significant benefits to using beam and block. “It’s a cost-effective technique and it doesn’t come with the risk of settlement, which a full ground-bearing slab can,” says Chris Parsons.

Section through house© Section through house

It seems like a lot more work to me, and creates a 1 foot high inaccessible void under the concrete that I would think would be occupied by other animals pretty quickly, but Ben advises that there is no way for them to get in. I can see advantages also that the insulation can be on top of the slab, which might help in allowing alternatives to foamed plastics.

This is a house that is built to last, using traditional and common technologies modified for Passivhaus efficiency. Above grade, the house is a cavity wall with insulation between two wythes of lightweight concrete block, held together with special ties that do not act as thermal bridges. The exterior is finished in lime render, which has a far lower carbon footprint than cement as well as other benefits:

Aesthetically it is arguably more visually attractive, it is more flexible and is more breathable allowing free transport of moisture through the building, creating a healthier environment.

It is an ancient material, and evidently is no longer made with bone ash, urine, beer and cheese.

boiler in laundry roomBoiler in laundry room/ Lloyd Alter/CC BY 2.0

Being a tightly sealed and super-insulated Passivhaus design, the entire house is heated by a tiny little gas boiler that also provides domestic hot water. Ben chose gas because a) it is common and accepted practice in the UK and b) those pesky neighbours might have been bothered by the noise of an air-source heat pump.

Living roomI apologize for not fluffing the cushion/ Lloyd Alter/CC BY 2.0

Because there is so little heat loss, the entire living area has just one radiator.

hood in kitchenPop-up kitchen exhaust hood/ Lloyd Alter/CC BY 2.0

There is a generous kitchen with induction range and an interesting pop-up exhaust fan that actually looks like it might even work.

Guest bedroomGuest Bedroom/ Lloyd Alter/CC BY 2.0

Planning ahead to when stairs are a problem, but also planning for guests, there is a comfortable ground floor bedroom with generous accessible bathroom.

View from Master BedroomView from Master Bedroom's deck/CC BY 2.0

Upstairs is Ben's office and three bedrooms. The master bedroom has extraordinary views over the English countryside.

Ben with HRVBen with HRV in Garage/ Lloyd Alter/CC BY 2.0

A key component of the operation of a Passivhaus design is the Heat Recovery Ventilator, which brings in fresh air, warmed by the heat of the exhausting air. I was extremely surprised to find that Ben installed his in the garage. I have written in the past that houses should not even have attached garages because of the possibility of exhaust and other fumes getting through the wall, and here, the entire ventilation system for the house is in the garage. It met with the approval of designer Alan Clarke, whom I respect tremendously, but I suspect there is going to be a lot of discussion about this.

The most impressive thing about this entire project is that it happened at all. The finding of such a gorgeous site after so many false starts, the approval process, the design and construction all as a self-build, is a remarkable tale. You can't help but be impressed with the solidity and quality of the build, especially when coming from the North American wood frame world. Ben Adam-Smith has built to last.

The other great thing about this house is that Ben has documented it with photos, videos and podcasts. It was not just an education for him but can be one for everybody thinking about building their own house. Dig in at House Planning Help.

How to build your own Passivhaus in 231 easy lessons
Ben Adam-Smith of House Planning Help shows how it's done.

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