Energy Conservation

Jon_2

Throwing this out for comments: 2500 sq.ft. single story home with full basement. Projected heating system, radiant w/recovery system on exhausted air. Located in northern NY on St.Law. River. Owner wants min. heating costs and will go for max. insulation to achive. 20% of building facing north is glass appox.
Question: What kind of insulation and how much for min. cost in heating bldg.?
Basement floor?
Basement walls?
Wall insulation?
Ceiling insulation?
Type of glass construction for windows?

GMcD

Not just insulation

It also depends on the type of structure. You also have to minimize thermal bridges around edges and openings and at all exterior walls exposed to outdoors. Glass should be minimum triple pane, low-e, or Heat Mirror 3-element low-e. If the budget can take it, ideally 4-element Heat Mirror would be about the best, highest performance window you can get in North America right now. (However, argon and krypton gas fills will help with thermal transmission performance, but I personally don't like recommending exotic gas fills due to leakage and sealing issues). Where is the rest of the glass? Ought to be some shaded glass facing southwest to grab some passive solar in the winter.

The only way to truly do a cost-benefit study on the insulation on various surfaces is to do a whole house energy balance using a full year of weather data. Passive solar gains in winter come into play, as well as daytime to nightime outdoor temperature differences.

The location of this place is in a heating-dominated climate zone, so heat losses will be the dominant issue. Basement walls and floors ought to be OK with R-15 styrofoam type insulations (on the ouside of the concrete to keep thermal mass inside the building). Exposed walls and roofs should be at least R-28 insulation with perimeter and stud spaces thermally broken (staggered stud details) to minimize thermal bridging at the exterior walls.

Remember to do the calculations to show that the capital costs for the better envelope and glass will also save $$ on heating plant size and infrastructure as well as the on-going operating costs.

Weblinks: http://www.southwall.com/products/heatmirror.html

http://www.cwc.ca/design/building_science/thermal_insulation/

jerry scharf_2

Been toying with an idea

Geoff,

You seem like the perfect person to bounce this off of. Handling the construction details of staggered stud walls has always seemed difficult to me. I came up with a slightly different idea on how to reduce the thermal bridging, but didn't have anyone to bounce it off of.

My idea is that you build a standard 2x4 exterior wall, then run 2x3s horizontally and flat across those at 16" spacing. Then you foam the wall with low pern closed cell foam. The thermal bridging is only 22 square inches per stud (as compared to 144 for a standard stud.) It seems like a very simple addition to a stabdard framing job, keeps the wall thinner than a 2x6, and achieves R25+ in the field of the wall. If the bridge points are about R5, and constitute 1.5% of the wall field, this seems like a good simplification.

I haven't figured out a nice way to decouple the top and bottom plates or the inner frame of windows and doors. How are these handled with staggered studs?

thanks for taking the time to look at my musing.

jerry

GMcD

Wood frame construction

Sounds like you are on the right track Jerry. I am by no means a wood frame construction expert, I try to stay out of that end of the market....

The top and bottom plates will always be an issue with the conventional "stuff the stud spaces with insulation" methods. The trick is to get the insulation on the outside of those elements if possible. Otherwise, with the method you've described, at least you've minimized the amount of bridging in the wall from "fairly significant" to "low".

Bob Gagnon plumbing and heating

I have a customer

that had standard 2" X 6" construction with fiberglass then 2" high denisity foam, like they use on foundations, over the studs and under the sheetrock. without any studs. this house was tight. I took the heat out of one room and it was only 1/2 degree cooler than the rest of the house, 2 days later. it was below zero, up on a hill, the wind was really blowing and the outside wall felt like an inside wall. Bob

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jeff_51

staggard suds is easy

done all the time to minimize sound. 2x6 plate with 2x4 studs. You just frame door and windows like standard 2x6 framing. Other alternative is 2x4 exterior wall insulated with whatever and then celotex or similar panel for thermal break and then frame another wall in front. Have seen this done alot in old crooked bldgs to straighten up the site lines in the interior. No reason you couldn't do this. More moolah than staggerd framing though,
If you do the staggered studs, than DO use iceneyne spay in. Fills ALL the gaps.

jeff_51

just remembered

we redid a house that was built in the 1850's. Timberframe with double plank on the outside. No interior planking at all. Did four inches of ridgid foam. Drywall was glued and screwed onto the foam and into the exterior planking. Had to be real careful of screw length. Had logs with the tops flattened for the house's floor joists on about 4 ft centers. Kind of fun house to do. Real good heat loss numbers and very tight.

Steve McCarthy_2

low energy house

An issue to consider when you build a wall with lots of insulation inside the wall cavity is condensation within the cavity. Condensation can occur inside the cavity due to air leakage into the cavity and by diffusion into the cavity. I like the idea of using 2x6 and R-21 within the wall and then adding 1 1/2" foil faced foam on the exterior of the frame(7200 DD). The foam keeps the first condensing surface ( the sheathing) warm enough that condensation does not occur inside the wall cavity on the sheathing. There are lots of complicated ways to build a wall but most framers can handle conventional 2x6 framing. adding foam on the exterior is a simple way to reduce condensation inside the wall and boost the r-value and reduce conduction thru wood framing.
Attention to air sealing details like sealing the exterior foam, making elec boxes airtight, sealing the drywall to the frame will go a long way towards reducing air leakage. I see houses that have a lot of insulation but when I run a blower door, they leak like a sieve. Look at the wall with IR and it is a sight that would make the angels cry. Making walls airtight really makes the insulation perform.

Steve McCarthy / Starbright energy Services

kevin coppinger_4

A lot of talk....

about framing techniques. Would it not just be easier to do an ICF home? 2 styro either side of concrete web form? I have done a few of these very tight, no mold issues in the walls and very strong. Use a HRV for sure. Cost 1 customer $400.00 last year for heat and hot water in a 2000 sq. ft home. Just another thought...kpc

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Larry Weingarten

How about...

using foam core panels, or SIPS? That's solid foam up to a foot thick with OSB on both sides. Give the manufacturer a plan and they can make you a "kit". Problems with moisture and thermal bridging don't happen if all seams are well sealed. The only real downside is finding a place to put wiring, plumbing etc.

Yours, Larry