Major Thermal Bypasses – The Big Holes in Your House

by Erik North on November 14, 2012

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First, a bit about my writing…I write longhand whenever I have spare time. Between audits, at lunch, after the gym when stopping for a coffee then I type them up. The thing is that I find a lot more spare time in my walking around day than at the home/office. To say there is a bottleneck getting them into electronic form is a disservice to good flowing bottles everywhere. This is by way of explaining an upcoming sentence.

Second off, ‘Major Thermal Bypasses’ is building geek for ‘holes’ in your house where you’re losing an abnormal amount of heat. More formally, they are areas in standard construction where flaws in the building enclosure bypass the thermal control layer.

Thermal Bypasses – The What and Where

The building envelope is those elements (walls and roofs) which separate the comfortable interior from the potentially uncomfortable exterior. Especially today where it is 98 F out…in Maine (<------ That was the sentence). A huge part of an energy audit is inspecting the building envelope for issues. And thankfully as builders have standardized their building practices, they've been considerate enough to standardize how and where they make giant holes in the building envelope. Thanks, guys! Thermal Bypasses and The Homebuyer’s Dilemma – Thermal bypasses like I mentioned are inadvertent holes in the building envelope. If one were to conceive a perfectly insulated and air tight house (with an appropriate level of fresh, ventilated air…no suffocating), it would be very simple. Make it like a box.

Wait, you want to get inside?!? OK, we’ll add a door. And you want to see the ocean view you paid an extra $100k for? Well, they’re have a really lousy R-value compared to walls but I suppose we can add a few windows. And a cathedral ceiling and recessed lights and a hot tub and a finished room over the garage and a zero clearance fireplace and a giant hole in the wall for fresh air (wait a minute).

You see where this is heading. Homebuyers have wants and needs and they’re most often at cross purpose with an easily defined building envelope. And the harder the building envelope is to define, the harder it is to keep the uncomfortable outside away from the comfy interior. When developing their housing certifications, Energy Star put together their list of common thermal bypasses.

List of Thermal Bypasses
Thankfully, the good folks at the Department of Energy have collected this info in one place…And here’s a link to the Energy Star thermal bypass list.

– Knee walls like those found in Cape Cod style houses.
– The ceilings over porches
– Attic hatches
– Zero clearance fireplaces (I love these because it is entirely enclosed and not evident to the naked eye)
– Skylights
– Garage ceiling joists attached directly to the building framing.
– Attic stairs built into exterior walls
– Bathtubs and showers built into exterior walls
– Cantilevered floors like those found in Garrison houses.

And the hits just keep on coming. Check out Energy Star’s list of thermal bypasses and take a look around your house. Fixing one of these issues can be a real heat and money saver.

{ 2 comments… read them below or add one }

Jeremy Marin November 26, 2012 at 9:08 pm


Do you take requests? Can you write something more about skylights and their problems? (Insulating problems more than water issues.)




Erik North November 27, 2012 at 7:13 pm


Thanks for the comment. Sure, I’ll take requests. I can’t guarantee when I’ll get to it but definitely.


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