Guidance based on the selected code edition and steady-state monthly analysis. It is not a compliance determination, the adopted local code and the authority having jurisdiction govern.
Wallcalc works out how a wall actually performs once it is built: the heat that gets through it, the temperature at every layer, and whether water vapor will condense inside it over a winter. It runs entirely in your browser, needs no account, and nothing you enter leaves your machine.
Because the studs conduct heat around the insulation. A 2x6 wall filled with R-21 batts does not perform at R-21: at 16 inch spacing the framing is roughly a quarter of the wall area and conducts far better than the insulation beside it. Continuous insulation on the outside is the usual fix, because it covers the studs as well as the cavities.
On the first cold surface the moist indoor air can reach, which in a stud wall is normally the inside face of the sheathing. Whether it happens depends on how cold that face gets and how much vapor reaches it, which is why insulation on the outside helps twice over: it raises the sheathing temperature as well as the R-value.
It depends on your climate zone and on what else is in the wall. The IRC sets out which vapor retarder class is required by zone, and allows a lower class when there is enough continuous insulation outside the sheathing. In Canada the NBC rules differ. The tool applies the rules for the location you choose and tells you which clause it used.
Yes. Set the wall type to basement, give it the height above grade and the depth below, and the buried part is analyzed against soil temperatures that lag the seasons with depth. The code checks switch to the basement wall rows.
It is free and there is no account. Designs are kept in your own browser. A share link carries the whole design inside the link itself, so nothing is stored on a server.
Wallcalc is an engineering aid, not engineering advice, and it does not certify compliance with anything. It models a wall; it does not know your site, your materials as delivered, or your workmanship. Have the assembly reviewed by a licensed design professional, and check it against the code your jurisdiction has actually adopted, which may be amended locally. Where this tool and an authority having jurisdiction disagree, the authority is right. Full terms of use.
Built by Jay Lyon, a software developer and
mechanical engineer in Burlington, Vermont.
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