Renovation Turns Old House Into Green Healthy House With Near Zero Heating Bills
all images and videos by Lloyd Alter
We know that almost half of our energy is consumed by buildings, and there are a lot of concerns about what to do with our older housing stock. In Kitchener Ontario, a non-profit called REEP (Residential Energy Efficiency Project) is doing an interesting experiment: They are taking two almost identical century homes and renovating them. One with a light touch, investing C$ 25K and cutting energy consumption in half; the other, a no-holds-barred lets-try-everything and go for net zero energy.
In this house, REEP changed the furnace, insulated and drywalled the basement and filled the void between the lath and plaster and the masonry with polyurethane foam. This is something that I didn't think could be done; there is not much space, it is often full of plaster and I have been concerned that the expanding foam would blow the plaster off the wall.
But Ben Barclay of REEP tells me that they drilled a lot of holes, used a really free-flowing type of polyurethane, and then used a thermal camera to ensure that there were no voids. Then they changed the furnace and the lightbulbs and voila, the energy bill was cut in half.
Insulation Rule 1: Add a Sh!tload of the Stuff
Construction manager Ben Barclay explains the process. I apologize for forgetting my tripod.
Ben explains the basement. The walls are insulated with R-38 worth of polyurethane foam, seven inches sprayed between and behind 2 x 4 studs. A dimpled plastic drainage layer separates the insulation from the exterior wall; any moisture that penetrates can drip down and be picked up by the weeping tile laid inside the wall, which is then routed to the sump pump.
There is one section of the wall that they have insulated to R12, R24 and R38, so that they can meter the heat loss through each and show the savings that accrue to different thicknesses of insulation.
I would have thought that once you are framing the walls and drywalling and finishing them, the incremental cost of going from R24 to R38 would be pretty meaningless in the larger scheme of things, but the insulators charge by the inch, even though getting there, administration and cleanup cost the same. But notwithstanding this, they will still save a bundle; after spending C$ 18,000 to insulate their heating bill is projected to be $138, a saving of over C$ 2,500 per year.
The insulation is sprayed between the joists, sealing the house tightly. Note the silver insulation in the ceiling; they have installed radiant floor piping to the underside of the ground floor and installed a half inch of rigid insulation below. They have not used any spreader plates, just PEX fastened to the floor. I don't think it will do very much.
Four Ways To Heat a House (Five If You Count the Dog)
The house has four heating systems: solar hot water, a hydronic boiler, and a geo-exchange (geothermal or GSHP). They also have a big active dog, which when you have this much insulation, is probably all that you need. But this is a demonstration project to show the public what is possible, so they have thrown everything they can at it.
Power Pipes: Recovering Heat From Wastewater
A powerpipe picks up the heat from the second floor bathroom drainage and preheats the supply to the hot water heater. When water goes down a drain it doesn't just fall down the middle but sticks to the pipe because of surface tension; the powerpipe circulates the cold water supply in a coil wrapped around the drainpipe. It is purported to recover 25% to 40% of the energy. BuildingGreen says that "The energy savings potential can be significant, particularly in commercial or institutional applications with showers, laundry, dishwashing" but I really wonder how much it picks up from just a residential shower, particularly if one takes appropriately short ones.
The Exterior Wall Conundrum: Can You Have Too Much Insulation?
We used this opening for a door to discuss the issue of insulating old buildings to such high levels, a subject that is worrying not a few heritage architects. In most old buildings, heat from the interior drives moisture out of the masonry or stone and helps it resist the freeze-thaw cycles that we have in this climate. But here one can see the studs set 3" off the masonry and 7" of polyurethane sprayed right onto it. Not much heat is going to get into that masonry at all.
Ben makes the case in this shaky video that the gap between the two wythes will let air circulate, and that having one side of the wall completely open to the exterior will let the moisture evaporate out. I am not so certain, but there simply doesn't seem to be enough research yet about what happens over the long term. If anyone reading has experience with this, please let us know in comments.
I wrote to Michael McClelland, an experienced heritage architect and principal in ERA Architects Inc, and he responded:
We have similar concerns to you.
One issue is the porosity of the brick. It's fairly easy to do a porosity test and 19th century brick is quite porous. If porous brick is left cold and wet it may start to break up in freeze thaw cycles. This is why on some larger scale projects people use thermal buffer zones to ensure that the exterior wall retains some warmth.
Second and possibly more important issue is bridging. It is very difficult in an existing building to seal the building. So in this case does the interior wood framing not create some bridging to the brickwork? We have seen examples where joist ends rot because the moisture movement has been concentrated to very small areas of the wall. In a wall with less insulation the moisture movement through the wall is not concentrated and relatively harmless.
Here, the polyurethane sprayed around the joists makes a good seal, but the joists are supported in the masonry, with their ends embedded in it. But there is also a new 2x4 stud wall inside the masonry going right down to the basement floor, which is probably adding a good bit of support to those joists. Time will tell.
Should a Super-Insulated House be Sprinklered?
On the second floor, they are installing a test section with polyurethane, glass fiber, denim and cellulose insulation, which they will be metering heat loss to show the public how the different materials perform.
There are good reasons why one might chose a different insulation; the stuff is highly flammable. According to Doug Stewart of Federated Insurance of Canada, some insurers nickname the stuff "solid gasoline." (PDF Here) He writes:
"When heated, polyurethane gives off a highly combustible gas. This gas will cause an instant flashover, putting life and property in danger. The thick, black smoke obscures vision and causes asphyxiation. Once a polyurethane fire is started, there is usually a total loss of the property."
However even he admits that when it is protected by drywall, it is "an effective and safe insulation."
I would go one step further, and suggest that if one is doing such a major renovation, the incremental cost of putting in a residential sprinkler system is not that big a deal. But then I think that we should Put Sprinklers in Every Housing Unit, as does does the International Code Council.
Kierkegaard on REEP
To paraphrase Soren Kierkegaard, "Patience is necessary, and one cannot REEP immediately where one has sown." It is going to take some time to see how this works out, what are the really worthwhile things and what are not worth the money. But the great think about this project is, that is exactly the point; to monitor it and watch it and test it.
This is a fascinating project; Cheryl Evans explains why REEP is doing it. There are so many different approaches to such a problem, and REEP has done a fabulous job of building a project that is designed to inspire people to make their homes greener, healthier and more efficient, whether they have $ 25,000 or $ 250,000 to spend. Graham Whiting of Whitingdesign had a lot of difficult choices to make, and I mean no criticism in my comments about the exterior walls and the sprinklers; we are all learning as we go here. I will visit again when it is complete.
More at REEP