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What is the best angle for a skylight on a low-slope roof in Chicago?

I am replacing a 30 year old plastic bubble skylight as part of a major remodel. The skylight is located a flat (low slope) roof in a typical Chicago small residential building and serves a third floor bathroom. The skylight will not be openable.

I have searched this site, the web, and the manufacturer's installation information, but am still unsure how to orient the skylight to maximize its benefits, while reducing drawbacks, like unwanted heat in Summer. It appears that the only requirement is that the skylight be installed at a slope greater than 15 degrees.

I have found on this site and other places, the advice that South-facing skylights be installed an an angle equal to the latitude plus 5 to 15 degrees. However, should the skylight be oriented to the South at all? It would seem orienting to the East would be a better choice: The bath would get the advantage of morning light, and avoid direct light from the South, and especially west, during the hottest parts of the day.

I have the option of orienting the skylight North, South, East, or West.

Asked by Dan Nehm
Posted Sat, 04/19/2014 - 08:40

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2 Answers

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1.
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North facing gives light with less heat. There are summer shades too. Velux sells what you need.

Edit, I do like your East facing idea and would go with that.

Answered by aj builder, Upstate NY Zone 6a
Posted Sat, 04/19/2014 - 17:56
Edited Tue, 04/22/2014 - 09:33.

2.
Helpful? 0

Dan,
in a heating climate like Chicago, the overall benefits of having south facing skylight in a flatroof are beneficial - even when using a 30% Solar Heat Gain coefficient. It would be even better to use 50% SHGC glass and an exterior shade in the summer - which gets you the best of both world - gains in winter, while still providing daylight in summer.

Velux skylights are meant for pitched roofs, so you will need to build a sloped curb to install them. This curb needs to be insulated and airsealed - an easier and better way to deal with flatroof skylights is to use one of the products we distribute with www.foursevenfive.com - in this case the LAMILUX skylight with insulated curb and frame.

Answered by floris keverling buisman
Posted Mon, 04/21/2014 - 12:22

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