Skylight replacement
MichaelLPrentice
| Posted in General Questions on
How can I determine whether replacing 23 yr old Velux skylights with new Velux (solar-powered ‘fresh air’) skylights is worth the high replacement cost? Any tips on energy savings would be much appreciated.
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Search and download construction details
Replies
Which climate zone are you in?
We are in North Central Mass . This is a continental, humid climate. Winter minimum temperatures these years are in the teens, but can go negative.
I don’t have an answer but wanted to follow along because I have 40 year old Velux skylights with failed insulated units and I am considering replacing the insulated units vs full windows.
I have three Velux roof windows that are about 4’x4’ and one that is smaller.
Estimated cost for just the insulated units is about $1600-$2000 with low e glass including install.
Estimated cost to replace windows completely is about $4000 PLUS install.
What did you decide for your situation and did you determine if there was any energy efficiency benefit?
The fancy solar business has no payback
Do you really open them?
All skylights are the worst, horizontal glass doesn't work that well.
If you can look up the stats on the old skylights you can probably figure out the payback, but if they are not otherwise problematic, it is not a cash flow winner
The payoff is to replace the skylight with a solid roof. I can't believe the code still allows them.
There are some places where they really make a difference. I have an interior room that was dark like a cave before I installed a few skylights, and now that room feels like "part of the house". Much nicer. The energy penalty of the skylight is worth it in this case. Remember that there is more to design than just energy efficiency.
For the OP: I doubt you'll have a payoff here. This is similar to replacing old windows: unless the old windows are REALLY bad (leaky single panes, basically), upgrading the windows doesn't usually make enough of a difference in terms of energy efficiency for the increased energy efficiency alone to ever pay for the upgrade cost of the windows. There can be other aesthetic improvements though that may be worth the cost. Skylight replacement usually only makes sense when the skylight is failing for other reasons, such as leaking when it rains.
The solar part has always seemed like a marketing gimmick to me. I usually just use fixed skylights in the few places I've used them, since those are much cheaper and less trouble down the road. The only place I could see a powered unit making much sense would be in a very high ceiling where it's very difficult to reach to operate any other way.
Bill
Thanks for the comments Bill. If you have time, we'd be very interested to know what factors would persuade you to use a skylight that opens. In our situation, the skylights (M08) are easily reachable. One other factor is that we are putting a 12K mini-split into this upstair room which otherwise gets very very little air through old leaky ducts.
If the skylights are accessible, I would consider one thing that would make operable units nice: Do you have another set of operable windows down load in the same room, or nearby? If you do, that's a huge plus -- you can now open those low windows, then open the skylights, and get cross flow convective ventilation through the room, which will cool it down quick in the evening, and let you bring fresh air in very easily.
In every other case (difficult to reach skylight locations, no other operable windows, etc.), I would use fixed skylights instead. The reason for this is that fixed skylights are far less likely to leak or have problems over time. I have had operable skylights before, and even in areas where we did have other operable windows, I found that we only rarely ever opened the operable skylight (maybe a few times total over a period of several years). It's just too much of a hassle to mess with the skylight, especially if it needs a pole to operate it, so we found we just used the windows only and left the skylight closed almost all the time. A power operated skylight with a remote control would probably get the unit used more frequently, but without the ability for air to come in somewhere nearby, you don't really get as much ventilation benefit as you might expect, so the operable skylight needs to be used as part of a system of operable windows to really be useful.
Bill
I agree lose the skylight if the room lacks windows install a sun tunnel as it will provide more light and leak less energy.
Seems to me operable skylight would only be useful in a climate where your windows were most often open and that does not sound like NC to me.
Walta
Thank you to all that commented! If anyone has a Velux MANUAL skylight, we would be very interested to know how difficult/easy it is to operate (size= M08). The 20+ yr old Velux that we are replacing are opened manually but this has become very difficult. The regional (W Mass) Velux rep and supply shop do not have a manually opening window to demo (Monopolies are terrible). On the other hand, how reliable is the solar battery powered window opener? We are looking into sun tunnels as well but it is the skylights that make this loft room habitable.
"How can I determine whether replacing 23 yr old Velux skylights with new Velux (solar-powered ‘fresh air’) skylights is worth the high replacement cost?"
Are you talking about energy savings from a better-insulating window, with a lower U-factor? If so, generally the energy savings don't pay for the cost of the replacement. I don't suppose you have the U-factor of the existing window? That would let us estimate energy savings.
I considered a sun tunnel at one point, but then I just put in a bright overhead light, with a daylight-temperature bulb. Pretty much the same feeling, minimal installation cost, and I don't lose/gain lots of heat through the ceiling.