Where's the Heat

It's 15 degrees Fahrenheit. Do you know where your heat is?






The picture above is of a roof in west Michigan in the middle of February. What's not snow

covered on the roof is a skylight. Good for letting light in. Good for letting heat out. Bad for utility

bills.


Why? Despite the claims by the manufacturers that they are energy efficient, they're not. A typical

R-value for a skylight is between 1.5 and 3 (that's being generous). We aim to have at least R-44

and prefer R-50 (more on R-value in another post) when we can. That's what suits this climate. We

work hard to seal the attic to reduce air movement (warm air going to cold). That's why the roof is

snow covered and the skylight is not. Since it had very little R-value, the rising heat melted the

snow.


Daylighting does help reduce energy bills because you're not turning on lights. But a roof is not the

place for a window.


What happened? Overall, it's a nice looking house, it's just not sitting correctly. This house plan did

not respond to it's site. It wasn't oriented properly. The skylight faces south, but on this side of the

house, there is the garage and an entry door. No windows in the south walls. And think of what

that window on the roof will do to the comfort of the home in mid-July. The garage could have

easily went on the north side, allowing for daylighting to come in from the south. In absence of

that, a sun tunnel would have been a much better option (those are about a foot in diameter and

puncture the building envelope dramatically less). They also have a diffuser at the interior that is

somewhat air-tight and reduces heat flow up the shaft.


The lessons: Have a home plan that will respond to it's site. Any good building designer will put the
home on the site to take advantage of daylighting. They will also design overhangs to block out the

hot sun in the summer and use it for passive solar gain during the heating season.


Remember: Windows go in walls.

Posted by COASTLINE BUILDING at 2/28/2008 2:04 PM
Categories: Energy
Tags: green building energy efficient building energy efficiency Energy efficiency building
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  • 4/21/2009 12:55 PM COASTLINEBUILDING.COM wrote:
    Green Builders should be wearing their colors today, right? I hope so. I also hope they're remembering why we do it. In the Kalamazoo area, Green Building should be focused on home performance. Actually, any Green Building anywhere should be focused on the performance of the home. The building scientist have been preaching that for decades. Unfortunately, what gets covered in the press are accessories, the expensive stuff. Solar and wind power, to name a few. Read this: http://www.buildingscience.com/documents/insights/bsi-007-prioritizing-green2014it-s-the-energy-stupid?full_view=1. I make this required reading when discussing a project with clients. I'll highlight the important points if they would like, but ...
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