Making a renovated building energy efficient
Hi all,
We’re in the building phase of completely renovating a chalet in Quebec. We are adding a floor, so the chalet will be two levels, about 1200 square feet. There’s a 4′ crawl space and no basement (we’re on Canadian Shield) and the chalet is facing south at the top of a slope to the lake. The contractor has done a number of similar renovations and is great to work with. I’m not an expert and don’t want to exasperate him with suggestions, but since concrete is being poured in a couple of weeks, and insulating and windows have not been installed it was suggested I post here.
Here is the floorplan and one elevation. There’s only been one modification so far; there will be windows across the kitchen facing the lake. We may revise the room proportions on the main part of the second floor.
I’m specifically concerned about heating and heating costs. The winters get quite cold and windy here, and even when we’re not there the house has to be kept at 12° C. Due to last-minute local requirements, we had to change the roof from a nearly flat to significantly peaked roof, and because our septic system is only for three bedrooms, we weren’t permitted to close up a couple of rooms (even though we only intend to use them as offices). The net result is while the home is not large, it will have lots of open spaces and 16′ ceilings at their peak. Since we’re facing a lake, we specified lots of large windows; 16′ of separate 7′ high windows in the living room. The windows are all low-e argon. There are trees at least screening the windows so we will mostly only get direct sunlight in the winter. As far as I know, spray foam insulation will be used throughout the building structure, which also has structural benefits.
For heating, the current plan is baseboard heaters and an air circulation system from the fireplace across the house. There will be an air exchanger and a vent at the peak of the ceiling will be used to recirculate warm air.
The concrete is being poured around the house, but it costs very little to add a concrete foundation to parts of the ground floor. So one thought is to use something like Flextherm XPress to heat the floor of the kitchen. We would then have three systems; fireplace, heated floor (which would retain heat) and baseboard heat. The kitchen and fireplace are at opposite ends of the main floor. There are sometimes power outages so I thought the retained heat would be valuable, as well as possible general efficiency and comfort from a heated concrete floor (which would have tiles over it). The Flextherm system also has an internet thermostat option, so we could increase the heat when we’re an hour away.
One idea is to decide on current electric options, and in the future have an energy audit and possibly install a heat exchange type system (which I understand may not be effective when it’s really cold). However, unless it’s a huge difference, and while a few days a year air conditioning would be nice, I want to avoid anything with overbearing fan noise.
So I hope this is complete enough for advice, specifically about saving heating costs while not compromising comfort.
Thanks!
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Replies
David,
Your question is vague. It sounds like you are looking for "advice about saving heating costs." That's a very general goal (but a good one).
You wrote that you plan, in the future, to get an energy audit. That's backwards. Step Number One is to get an energy audit. Do it now. Your energy rater will provide you a prioritized list of energy retrofit measures.
My guess is that the audit will recommend air sealing measures. Other possible recommendations include insulation improvements.
If you are buying new windows, you may want to consider upgrading from double-glazed to triple-glazed.
Hi Martin,
Thanks for the response. Sorry it wasn't clear.
There will be very little left of the original 1960s one floor building. The wall insulation, coverings, and many structural elements are being re-done (this really is a substantial renovation) so will have completely new spray foam insulation, which I understand performs well in cold weather (random GBA link).
I'm actually mostly wondering about the heated floor option; if it's worth the increased up front cost in terms of benefits (in addition to being more comfortable), though other advice is appreciated.
I will ask if the windows will be double or triple glazed.
David: Energy issues need to be designed in, not added on at the last minute. If you are concerned about energy efficiency, you need to make decisions about insulation, air sealing, windows, ventilation. What you decide will depend on budget of course. But you need to educate yourself and not rely on your builder. For example, most triple pane windows are better than double pane, but not always. Window specifications will tell you how efficient they are. The lower the U value, the better. U-.15 is good, U- 30 isn't.
Spray foam insulation has its place, but is often far more expensive than other options, especially if thermal bridging isn't addressed.
The best advice I can give is to learn as much as you can and consult with someone (architect, energy rater or..) to help make decisions before construction progresses and it's too late. Green Building Advisors is a great resource. Keep coming back with your concerns and questions.
Thanks Stephen. Though I was mostly wondering about the heated floor, I am also looking for starting points and emphasis here. I am not an expert and with my work schedule can't do more than dabble in this topic (which may not be helpful), so realistically have to rely on the builder. But I am going to ask about a pre-construction energy audit and window rating.
David: I've lived with a heated floor. I wouldn't do it again, for several reasons. Radiant heat is more expensive to install than other options. For a house that isn't always occupied, the slow response time when you want to turn up the heat is a real disadvantage. If you rely on solar gain for heat on sunny days, your radiant heat turns off and then when the sun goes down it has to catch up. If you take this opportunity to make the house tight and well insulated, you won't need much heat, whatever system you install.
My new house has unheated concrete floor and we're always comfortable. I'd spend the money you'll save on making the building envelope better.
One comment on the evening cool down problem after solar gain goes away. This "catch up" problem can be avoided by installing a slab sensor to monitor the temperature of the radiant/concrete floor. You set a minimum floor temperature where heat comes on no matter what.
Yes, this is a bit trial and error, but once you have it down you are golden. In our house it's 64 degrees for the floor sensor and 68 for the air temperature. We have the slab sensor on the north "cold"/"shaded" side of our ground floor. Wiring exists for a 1st floor slab sensor, but we didn't seem to have much of a problem there, less continual heat loss unlike the ground floor slab. (Fortunately we discovered this issue during interior fit-out and still had a way to get the sensor wires installed.)
Thermostats from Tekmar offer this feature.
OK thanks These are very helpful. It doesn't sound like a heated floor is worth it if there's much up front cost and it's not a contractor specialty (though I'm sure they would be nice in the right conditions). I will emphasize the energy audit idea.
David,
You're right that if your work schedule is busy, and you're not an energy expert, you'll have to trust your builder.
Depending on what stage this project is at -- the planning stage or the construction phase -- you may want to hire an energy consultant to review the plans. In general, the most important thing you can do is to have an airtightness goal (for example, 1 air change per hour at 50 pascals) and to verify whether that goal is met with a blower-door test.
The second most important thing you can do is to specify insulation with an R-value that exceeds minimum code requirements. Many spray foam contractors try to convince homeowners that you can skimp on R-value when using spray foam. If you meet someone like that, be wary. (The advice stems from the fact that spray foam insulation is very expensive.)
The third most important thing you can do is to specify windows with a low U-factor.
If you create a tight, well-insulated envelope, the details of your heat delivery system become much less important than in an ordinary house.
Good luck on your project.
Thanks Martin.
I just upgraded to triple pane glass with a U factor of .13. One thing that was surprising is the vendor (Gentek) said the argon leaks 10% a year. That sounds quite a bit worse than what I've read. Regardless, the contractor felt it's a reasonable investment even with just the benefit of triple panes. I am travelling for the next while so can't reasonably follow up on further suggestions, nor can I delay work that's already underway.
It's difficult for the contractor because we came to him saying we wanted to keep the final cost down, but being a nerd (but not a building expert) I have been asking a lot of questions, which generally are underdeveloped or affect the budget. I completely understand him not wanting to feel constantly second-guessed, and am certain he has our best interests in mind, but I want to balance toward avoiding large electricity bills going forward. I believe we will next look into main floor insulation details. If you have specific suggestions about what to request for the main floor, like what specific R-value, I'd appreciate it!