Superinsulation

The Dumont House

The first time I saw Rob Dumont’s house I was unimpressed. I was visiting an ex-girlfriend in Saskatoon, I mentioned that I was doing some research into sustainable homes, and she said “there’s one near here, we should walk by it.”

It just looked like any other house. The Dumont house is in the colonial revival style, it’s simply built and doesn’t stand out in the neighbourhood, which has a suburban feel to it (though it’s not far from the downtown). I’m used to seeing half million dollar ecohomes, so when you take away the architect and expensive finishes, solariums, thermal mass walls, radiant floors, etc., it’s hardly recognizable as an ecohouse. I arranged to go back later and visit Rob Dumont, who gave me a tour of his home and some other projects he was working on. What initially turned me off about the Dumont House (because it challenged my preconceptions) now makes it one of my favourite sustainable homes.

16 inch double wallWhen Dumont built this house in 1992 it was one of the world’s most highly insulated homes – but the house, like Dumont himself, is understated. Dumont took the double wall system from the Saskatchewan Conservation House, stretched it out to a full 16 inch wall cavity, and filled this space with blown-in cellulose insulation (which is just recycled newspaper with borax added for fire proofing and pest control). There are about 16,000 lbs of cellulose in the house – but what makes this insulation system really special is that the two walls have very little framing between them, so there are far fewer pathways to lose heat through the wall, either through leakage where the insulation doesn’t meet the wood perfectly, or by ‘thermal bridging’ through the wood itself. It may seem obvious, but it needs to be said: wood is way worse insulation than insulation is. A 2×6 stud wall with R20 insulation batts has an overall insulation value of about R13. Rob Dumont’s walls are R60, the attic is R80, and the windows are R5. The whole house is carefully air sealed. It takes less than 1/4 of the energy to heat Dumont’s house that it would for a conventional house. In 2000 Dumont wrote an article describing the energy efficiency features of his home.

Hot water heat-exchangerAs we continued the house tour, Rob showed me some things that really could be added to any existing house. The first was a drain water heat exchanger, just a copper tube wrapped around the shower drain – as hot shower water comes down the drain pipe the cold incoming water in the coil is warmed. “On a shower it will recover about half of the heat that’s otherwise going down the drain,” said Dumont. He quipped that “I’m worried that with the price of copper, in a home invasion someone will steal it.” Still, barring home invasions, the economic payback is pretty quick – if your hot water heater is electric the heat exchanger will pay itself off in 5 or 6 years, with gas maybe double that. Next we looked at the hot water heater itself, which is a standard tank but wrapped with batt insulation and a thermal blanket adding up to about R28.“Without the insulation it loses about 100 watts of heat continuously,” Dumont said, “with the insulation it’s down to about 25 watts.”

Painting of the house by Phil

Because of the simplicity of the Dumont house, it wasn’t expensive to build. The insulation, upgraded windows, and a solar thermal heating system, added about 7% to the building cost. “If I’d put brick on the outside of the house instead of hardboard siding,” said Dumont, “the brick would have cost more than all of the energy conservation features. I’d much rather have an energy-efficient house than a brick house.” In fact, the energy efficiency finished paying for itself in 2008, after 16 years – now it’s turning a profit. And he pointed out other non-monetary benefits – no draftiness, no cold feet, and the nice aesthetic of the deep window ledges.

Rob Dumont, like many of the builders and designers I’ve met, started his work in the 1970′s, and spent some time wandering metaphorically alone in the desert in the 80′s and 90′s. “Society has got a very short attention span,” he said, “there are waves of interest, but mother nature bats last. I started working in the 70′s on the Saskatchewan Conservation House, one had to really keep the faith through a part of the time since, because not many people were very interested. I must admit back in 1973, with the oil shock, I thought the reasonable thing to do would be to change the way we do our houses radically. That was my youthful naivety at the time.” He showed me a book of solar homes that was written in the late 1970′s, a sort of hippie version of what I’m trying to do, and I realized that I’m just the latest emissary of societal interest, something Dumont has seen come and go. I feel like this time it may be different, but I’m not sure. “It’s encouraging,” said Dumont, but “it’s not nearly at the level I’d like it to be. EF Schumacher put it nicely, he said the wind may not always blow but at least we should have our sails up. That’s the way I feel.”

Rob and his wife Phil took me to see a college basketball game, in which the home team, the Huskies, thoroughly trounced the competition (both women’s and men’s teams). I pictured Rob in his younger days playing basketball, fit and idealistic, believing he could change the world. And he did – it just changes very slowly. I wonder, when I look back in another twenty or thirty years, how I will remember this time. As the beginning of real change, or as lost opportunity? All I know is that my visit with Rob Dumont left me more optimistic than when I arrived.

Harold Orr’s Superinsulated Retrofits

Recently I had the privilege of interviewing Harold Orr, who was the project leader on the Saskatchewan Conservation House in the late 1970′s. He was involved in the invention of the residential HRV, and blower door tests, and his work influenced the Passive House and Net Zero movements. Now in his eighties, his brain contains a library of information on energy efficient building, and he talked to me for two hours straight. Orr’s main passion for the past several decades has been superinsulated retrofits of existing buildings, and he says the need for deep energy retrofits was obvious to him from early on.

The Saskatchewan Conservation House, now seen as a milestone in energy efficient building, was finished in 1977. “We recognized that as a first step,” Orr tells me, “the next step was to see if we can do this on a larger scale.” The province of Saskatchewan organized a competition, in which builders submitted proposals for a showcase of energy efficient homes – the challenge was to design and build homes that use only 25% of the heating of a conventional house. Orr was involved, along with Rob Dumont, in evaluating the proposals, “but we realized even as we did this that the number of houses that we build every year in a city is a small percentage of the houses that are already in a city.” Only in cities with a major building boom can you achieve a significant energy reduction, Orr explains, “so we were concerned about how we might do this on a conventional house.”

Orr and Dumont started looking for a house to retrofit and study the results, and by the end of 1981 they had found one in Saskatoon. This was the same year that the Superinsulated Retrofit Book, by Marshall and Argue, was published, describing double wall retrofits. The house Orr and Dumont had found was a 1968 bungalow with 2×4 stud walls and 2.95 air changes per hour (slightly better than the average house of that era).

“We decided to do a major energy retrofit on the house, and we wanted to bring it up very close to the level of the Saskatchewan Conservation House,” Orr says. The whole process of this renovation is described in a report that Orr wrote with Robert Dumont. They performed blower door tests at each stage of the renovation to see how air-tightness of the house was affected. They took off the stucco and wrapped the walls with polyethylene, which was sealed down to the foundation and up to the top plate of the house, and not surprisingly the house was considerably more air-tight. Next they hung a second 2×4 wall off the exterior of the house, with an eight inch gap between the old and new wall. By the time they had insulated the cavity and the new wall, the combined insulation (including the existing insulation in the old wall) was about R50.

“That did the walls quite well, but we wondered what on earth to do about the roof,” Orr says. “Because one of the major problems in housing is the leakage between the house and the attic space.” Because of wood shrinkage there is nearly always a gap where the drywall meets the top plate, which Orr estimates is commonly 1/16 of an inch. Drywall is also not normally air tight at the floorline – so in most older houses air can travel behind the drywall, from the living space into the attic.

“So we thought why don’t we cut the tail end of the rafters off so it’s nice and smooth at the edge of the wall,” Orr recounts, “and we’ll put a piece of plywood over the raw edges that we’ve cut off, and then we can carry the vapour barrier that we’ve already put on the outside of the wall right over the roof and down the other side.” This is what is now known as the chainsaw retrofit – a time lapse of a later chainsaw retrofit was filmed by Orr’s son Robert.

“So anyway we’ve got the vapour barrier on the roof and we’ve got it tight,” says Orr. “Now we put 2×8′s, one at the edge of the roof, one at the peak of the roof and one half way in between. On top of this we put new rafters down the roof. In the 2×8 we put R28 and in the 2×4 rafters we put R12 which gives us R40 on the roof. Plus the insulation we already had in the attic which is likely around R20. Now the we’ve got R60 in the roof. We’ve got the outside walls of the house and the roof done, and we’ve got the house very very tight.” In fact Orr says that the 1981 retrofit was almost identical in its performance to the Saskatchewan Conservation House.

Orr has worked on a number of retrofits since, most recently a four-suite apartment in Regina. This renovation of basement, walls and roof had a cost of about 11$ per square foot for materials (including metal roofing), and about the same again for labour. Because the retrofit turned it from an undesirable to a desirable place to live, with commensurate increase in rent that could be charged, it has an eight year payback time – making it a phenomenal investment.

So the economics of the double wall, or superinsulated, retrofit are not bleak, though it’s a large investment, and finding the right contractor to do it is going to be important. But how does it compare to just tacking some foam to the outside of the house and re-siding it? According to Orr there is no comparison.

“I took four walls and assessed them,” Orr says. “One I put 2 inches of styrofoam on, at R5 per inch that would be R10. When you put 2 inches on you really have to strap it, because you cannot put siding on over 2 inches of styrofoam. And unfortunately 1×3 strapping is the same price as 2×4′s. So if you’re putting strapping on, why not use 2×4′s?” And why not center them away from the wall, for a double wall retrofit? Since foam insulation is so much more expensive than batt insulation, says Orr, “I can put in R60 for the same price as R10. Now you’ve got to persuade me that R10 is better than R60.” That’s just materials, labour will change that somewhat, but the point is made.

Orr has more to say, however, adding that “when you put styrofoam on the outside of a house you’re not making the house any tighter, all you’re doing is reducing the heat loss through the walls. If you take a look at a pie chart in terms of where the heat goes in a house, you’ll find that roughly 10% of your heat loss goes through the outside walls.”  About 30 to 40 % of your total heat loss is due to air leakage, another 10% for the ceiling, 10% for the windows and doors, and about 30% for the basement. “You have to tackle the big hunks,” says Orr, “and the big hunks are air leakage and uninsulated basement.”

Air leakage in a typical house, from Keeping the Heat In

“I think the problem is that people don’t properly analyze where the heat is going. Get the book called keeping the heat in, it’s a publication of Natural Resources Canada [available as a free download], and anybody doing any work of this type should get this book and study it. If you look at where the heat goes the big chunk is air leakage, and usually putting styrofoam on the outside isn’t going to affect anything.”

I close the interview by asking why, so many years after retirement, he’s still doing this kind of work.

“It’s a passion with me,” he says. “I enjoy it. And I’m enough of a scotsman that it bothers me to see people wasting their money. I go by houses every day and I see them putting on an inch and a half of styrofoam, and lord help me – why don’t you do something for the same price and do it better?”

More information

 

History of the Chainsaw Retrofit

 

The common origins of Superinsulation, Passivhaus, and Net Zero homes

A lot of valuable lessons were learned as a result of the oil crises of the 1970′s. Unfortunately in the 1980′s many of the conservation initiatives from the 70′s were abandoned – but the skills, knowledge and awareness garnered at the time were not lost, and we’re benefiting from them today. In building science big strides were made in insulation and air sealing of houses, and a lot of this knowledge came out of two projects in Illinois and Saskatchewan.

In 1976 a group at the University of Illinois at Urbana-Champaign developed a design which they named the “Lo-Cal” house, which used two adjacent stud walls, with alternating studs, to achieve R30 insulation and eliminate thermal bridging through the framing. The term “superinsulation” was coined by Wayne Schick, project leader, to describe the high insulation levels used in the walls, attic, and basement. Several houses, duplexes  and condos based on the Lo-Cal design were built in Champaign-Urbana, Illinois between 1977-79.

The Saskatchewan Conservation House was built in Regina in 1977, using similar principles but went further with R40 walls. Again the walls were built out of two stud walls, and the extra 10 insulation points were gained by adding a cavity between them. The whole wall assembly was filled with blown-in cellulose insulation. Another thing that these two projects had in common was a science-based approach, with extensive modeling of the designs, and monitoring of real-world performance.

One of the most important things that both the Saskatchewan and Illinois teams learned was that in most houses the heat is simply slipping through the cracks, and they needed to develop techniques to dramatically increase the air-tightness of buildings. When they realized they were removing all the natural / accidental ventilation from the house, the Saskatchewan team created one of the world´s first air to air heat exchangers, or heat recovery ventilators (HRVs). There´s now a global market for HRVs, and in most cold climate areas some type of air sealing is now required by building codes. In Canada the creation of the R2000 system (a voluntary system for building efficient homes) was credited to lessons learned from the Saskatchewan Conservation House.

The lessons of sealing and air exchange have been widely adopted, but the idea of superinsulating a house to R40 or above, or emphasizing passive solar heating, have remained relatively on the fringe. One of the people who noticed the Lo-Cal and Saskatchewan Houses was Wolfgang Feist, the originator of the Passivhaus standard – a very rigorous system of building that is popular particularly in Europe where there are some 20,000 certified passive houses. Feist lists Harold Orr, an engineer who worked on the Saskatchewan House, as one of his influences. And it’s probably no coincidence that Urbana-Champaign, origin of the Lo-Cal house, is one of the centers for the passive house movement in the United States.

Rob Dumont, one of the engineers who worked on the Saskatchewan House, went on to build his own house in 1990, which at the time was the most highly insulated house in the world. Surprisingly, the extra insulation, upgraded windows, and a solar thermal heating system, only added about 7% to the building cost. “If I´d put brick on the outside of the house instead of siding,” says Dumont, “the brick would have cost more than all of the energy conservation features. I´d much rather have an energy-efficient house than a brick house.” In fact, the energy efficiency finished paying for itself in 2008, after 16 years – now it´s all gravy.

Conrad Nobert, owner of the Mill Creek House in Edmonton had the same experience with cost. “We got 80 to 85 % of the way to net zero, versus a conventional home, for about 20 to 25 thousand,” says Nobert. “So you would call that a net 0 ready house.” When Conrad talks about net zero, he means that the house will produce as much energy as it uses, by balancing energy use with energy production from solar panels on the roof. It sounds easy – just keep adding solar panels until you reach net zero – but in fact very few houses have enough room on the roof, or even on the property, to compensate for the energy they´re using for heat and electricity. The Mill Creek House uses similar systems to the Saskatchewan House, only better – it has double stud walls, spaced 16´´ apart to get R60 walls, an advanced HRV, and triple glazed windows that are R8.

Peter Amerongen, who built the Mill Creek House, credits his career as a builder of super-insulated houses to a talk he attended about the Saskatchewan House. “I heard Harold Orr in 1978 and it just stopped me in my tracks,” says Amerongen. Ever since then, Amerongen has been building R2000 or better homes. Before building his first net zero house, Amerongen went on a pilgrimage to Rob Dumont’s house to learn what he could from it. Then he took it even further.

Likewise the Passive House movement has gone far beyond its inspiration of a few superinsulated homes built during the late ’70′s. But the original superinsulated homes should not be forgotten, if nothing else for their simplicity and affordability, as evidenced by Rob Dumont’s 7% incremental cost to build the world’s (then) most highly insulated home. What that tells me is that we should be building all our homes to a much higher standard. And I’m sure that change will continue to happen, slowly. Meanwhile the Passive House and Net Zero homes are the pioneers that we can look to for examples of how far we can go.

More information about the Lo-Cal House can be found in a presentation by Michael McCulley.