Would attaching a piece of plexiglass or plastic to a skylight to block the opening on the same plane as the rest of the ceiling conserve heat? with the 1/8 - 1/4 inch plexiglass extending a few inches extra over the edge. in the case i'm talking about the 'glass' bows a little bit in the middle which i would guess helps slough the hottest air to the side increasing efficiency.
the introduction of a ceiling fan complicates the equation. Does this slow the progress of hot air to the glass of the skylight window itself, or is the heat trapped up there shielded from circulating currents?
If you are trying to block "thermal gain," you will have to use a reflective curtain. That is the best way. The second layer of plexiglass will retard some of the convective currents but do little for heat gain into the space.
Are you trying "insulate" for hotter outside or hotter inside?
Are you thinking of a permanent installation or a seasonal installation which you take down and put up each year?
How high are your ceilings and how insulated are the ceilings themselves?
What are the dimensions and construction/installation details of the skylight?
Is this a planning/speculation question or do you have an existing skylight that's not doing what (or as well as) you want it too?
1/8 plexi is very bendy; 1/4 less so but still not very rigid.
Location: Zone 5 Brimfield, MA
posted 7 years ago
Thanks for responding,
Jay - Not sure what you mean by block thermal gain. we want to keep heat in the house during the winter, while still allowing sunlight to enter. Blocking currents is the goal since the plexi is probably not highly insulative, but can you explain in more detail why blocking hot air from easily moving to the highest and most heat conducting membrane between the cold air will not keep the room hotter? Conductivity seems like it would be a slower process than even passive convection in this case...right? but is it even worth the cost of the plexi over many years?
Rufus - Hot inside, installed during winters only, unless we decide it is not worth the hassle of putting it up and down, one ceiling is 8 feet, the other ceiling with a skylight (*the room with the woodstove) has a slope and a higher roof with the skylight mid slope. since you asked, they are already installed. i know thicker plexi will insulate better...but i forget which it is. I think the ceilings are well insulated. Do you think this would make more sense on a small or large skylight?
i think this could be tested by placing a thermometer in the skylight space and comparing with or without the plexi, if its colder with the plexi then the heat must be staying inside the room, because the plexi wouldn't encourage heat to leave any faster. however, i'm not going that far.
some permies like to nerd out on microclimates indoors and out, cheers
Sorry about that, from the way I read it, you needed it to keep from getting hot. Now that I understand, all you really need is a simple "clear vinyl" frame that will fit either over or just inside skylight casing, no real need for plexi at all. Think of it as some of the double wall green houses. They let light in, but the double wall insulates much better. If you want to experiment, get some clear 'bubble wrap." We did some thing similar many years ago and the results were interesting. You have to use enough but not to much. It will allow fro solar gain, but not loss. Just keep adding layers behind the vinyl till you get a balance.
You might try one of these ideas, they are easy and inexpensive. they create great dead air space.
I've used these window sealing kits for several years for various types of projects, including sealing of a skylight. In addition to creating a dead air space, they keep the window/skylight clean, too, saving time and energy of cleaning. THe kits come with double stick tape, clear polyethelene window film and little alcohol pads to clean the area where the tape will be appliced. Instead of using those pads, I use the natural cleaner I prefer with great results.
These films when applied, also diminish sound transference, interestingly enough.
In addition to sealing a skylight and the usual windows:
***One place I lived had a couple of windows, which due to their location, I wouldn't be opening.There was plenty of ventilation otherwise. So, I used the window sealing film on the interior AND exterior of these windows, thus creating an extra dead air space. The windows had a metal frame and the double stick tape stayed on for two years until I moved and took it down. THe windows were still clean.
***I've also used the film on doors--french door types--with glass panels, inside and out. Creating two dead air spaces.
***In the apartment we presently inhabit, there is a cold area just inside the door and a small alcove type space. So, I took the large lengths of film and draped them over a long tension rod to create a see-through air barrier. VOILA! it has significantly helped to keep the living room warmer.
I will add that there are times I use TWO strips of double stick tape. and other times I have also used clear shipping tape to help keep film attached to the frame. I may not have needed to do that, but I like to protect the time I invest in a project. Whenever I've used two rows of double stick tape, it always stays.
There are also some WIndow Inserts which folks have built with wood frames and this same poly film wrapped around the frame to create an extra dead air space. These frames slide into place. These types of inserts can be used when needed and stored away, when not in use.
I dreamed up this idea for my own windows and then that folks were already selling them online. Some folks charge $9 a square foot to build them as a business. Personally, I think this would be great local business for many folks, to help others in their areas.
Anything that seals the skylight and creates dead air space will improve the insulation of the skylight. Gail's clear film methods have to be the biggest bang for the buck; as she said, you can leave it on if the "opening" isn't going to open. With two people it's probably just as fast to install as anything else. Be careful on the ladder!