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Musings of an Energy Nerd

South-Facing Skylights: Threat or Menace?

Owners of sunrooms have developed a variety of ways to address their buyers’ regret

What's that material covering the sunroom skylights? Yes, it's Ice & Water Shield. Notice that the vertical windows are all equipped with shades.
Image Credit: Martin Holladay

There are two kinds of sunrooms: those that have sloped glazing and those that have only vertical glazing. Sunrooms with sloped (or in some cases, curved) glazing are more common (and, of course, more uncomfortable). In order to make sure that these rooms are sunny, they are often located on the south side of the house.

When homeowners flip through design magazines or visit the websites of sunroom manufacturers, they see photos of happy families enjoying their sunrooms. Once the sunroom has been built, however, reality sets in. In winter, the sunroom is cold. In summer, the sunroom is hot.

One way to address these problems is to build an insulated wall that separates the unpleasant sunroom from the rest of the house. That works, but it’s irksome to have to look at a $15,000 room that never gets visited.

Another way to address these problems is to run a huge duct to the sunroom, and blast it with hot air from an 80,000 Btuh furnace during the winter, and cold air from a 4-ton air conditioner during the summer. That works, too — but the energy bills are painful.

An ingenious solution to the problem of south-facing skylights

There are other ways to address this type of buyers’ regret, of course. I recently took a photo of a novel solution devised by homeowners in Vermont.

The home in question has a south-facing sunroom with three skylights — skylights that probably cost at least $2,000 to install. After suffering from several years of overheating, the owners simply covered the skylights with Grace Ice & Water Shield. Problem solved.

Martin Holladay’s previous blog: “Polyethylene Under Concrete Slabs.”

Click here to follow Martin Holladay on Twitter.

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  1. GBA Editor
    Martin Holladay | | #1

    Response to Dan Kolbert
    Maybe you're right -- maybe these are PERSIST skylights. If so, the homeowners must be waiting for the spray foam contractor to come and install 4 inches of foam on top of the Ice & Water Shield.

  2. STEPHEN SHEEHY | | #2

    In my present house, we have a sunroom measuring 28 x8, on the south side of our zone 6 house. There are large, cheap double pane, double hung windows on the south side and a door and window on the west side. Three non-opening skylights. We have a wall-hung propane heater that we hardly ever use.

    It works pretty well. In winter, it collects plenty of heat from the sun, such that on sunny days, we o pen the French doors to the conditioned space to heat it. We can keep hardy plants out there in winter, such as rosemary, which would be killed outside. The temp doesn't get lower than about 20 degrees F even when 15 below outside.

    In summer, on really hot days it can get uncomfortable, but in summer why would one want to sit in an indoor subspace? When the sun goes down, the open windows cool the room down quickly and it is a very comfortable place.

    My point is that it is relatively cheap space that gets used a lot. It was never meant to be part of the "indoors."

    In our new house, we're doing a similar room, although with better, but not best, windows. We expect it to be a nice winter space on sunny days and to function as an unheated greenhouse where we'll start plants in early spring. The interior walls adjacent to conditioned space will be the typical exterior walls, fully insulated with PH level windows and air sealing. Concrete floor. Again, we expect it to function as a screened porch on summer evenings.

  3. dankolbert | | #3

    I like it
    PERSIST skylights. Bet the air-sealing on those babies is fantastic.

  4. user-3549882 | | #4

    Skylights in general, not just sunrooms
    Thanks, Martin. Good topic.

    We don't have a sunroom but we do have skylights. If we had a sunroom, I'd think about it like Mr. Sheehy does, namely to view it as an occasional use space and not even try to make it part of the indoors. I think this applies regardless of which way the sunroom faces.

    We do have skylights over our family room.!outside-view-3/c1ehf

    It's a nice aesthetic. You get additional natural light where it's not expected. You notice them and then your attention wanders elsewhere. No one I know gazes out a skylight for hours to take in the view. The view is usually of the sky or maybe a tree branch. Meanwhile, the skylights let out the heat in the winter and scoop it in during the summer.

    My solution was to keep the skylights and to moderate their effect. I created an acrylic insert- in- frame that mounts into the skylight cavity inside. This creates a dead air space for increased R value. You don't even notice it's there. The insert is removable but is left permanently in place. For summer, I installed a solar grate to lie atop each skylight. It's 'install and forget' and no operational adjustments are needed. The grates are surprisingly robust. After 10 years, virtually no maintenance. It changes the view but it lets in plenty of desirable natural visible light while blocking most of the undesirable infrared that would otherwise add to the a/c load. The grates are stored in the Fall to allow the free sunlight heating effect.

    If I were building new I'd pass on the skylights and other stuff like a swimming pool. Been there, done that. But when it's part of what you already own, you do the best you can and then read the GBA blogs to see if anyone has an idea you can use.

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