vacation home winter solar gain / insulation

[sailor27]

Lake home 1 1/2 stories with basment (near Erie Pa) recently renovated with a honeywell heatpump with electric backup. House set at 55 degrees.Question leave windows and skylites covered (insulation) or Open (solar gain)?? Thanks GENE

[pstu]

You did not specify whether the windows faced North, East, West, or South. That would affect the heat gain quite a lot, I think the heat loss would be relatively unaffected. You can see there is some guesswork involved.

It is my guess that the heat loss would far outstrip the heat gain on a daily basis. My own house has lots of window area, but they are mostly shaded, and heat loss is a huge part of winter behavior here. If you could read your electric meter on a daily basis for a few days, and weather was comparable a couple of those days, you could perform the experiment and possibly the results would tell you for sure.

Keep in mind I am a homeowner far away from your region, in S.Texas, and I will be listening to hear if any pros have a different opinion.

Regards -- Pstu

[cem-bsee]

for solar gain:
there must be sunshine,
there must be something to absorb energy. say dark bricks

[t527ed]

i would say the gain you would recieve for the few hours a day the sun was in the right position would be lost many times over by the loss the rest of the time.


i say cover them up.

[wyounger]

How much heat you can hold in with a window treatment depends on the window treatment. Curtains work better than blinds. If you don't think curtains can act as insulators, you haven't been to a house that only had problems with wintertime condensation on the windows when the curtains were closed.

Solar gain definitely requires sun, so you really only have a shot through the unshaded south-facing windows in this case. You will get a nontrivial amount of heat gain by leaving those windows uncovered, so I'd vote for covering all the windows but those facing south. The sun is low in the winter, so it will get in just fine under almost any overhang, but the flip side of that is a big pine tree or another building in just the wrong spot can totally steal your solar gain.

In an ideal case, you'd have the house oriented to face south, biggest windows on the south side, black floor inside the windows with lots of thermal mass to absorb and re-radiate the heat inside. But the thermal mass is done more so you still have some heat around to get through the cold and dark night in an occupied home. In the real world, you can still gain lots of heat with the sun shining in through those windows on ordinary carpet, furniture, etc., and with the place vacant, the thermal mass isn't make-or-break.

As for the skylights, I'd cover them unless they face south and are angled enough to let some sun in. Those facing any other way probably will be net heat losses in a northern winter. You don't get solar gain from indirect light, you get it when the sun shines directly in a window. Just ask your cat where the sunbeams are (she will know) and make sure to let them in :)

[dan sw fl]

Originally posted by sailor27
House set at 55 degrees.
My guess is Covered!

Q = ___ U A dT
55 ___ Inside
30 ___ Outside Mean Daily High 40 Low 20
25 ___ dT

Q = ___ U * __ A * dT
150 __ 0.6 __ 10 __ 25
BTU/hr
18 ___ hours
2700 _ BTU/day heat loss ___________________

______ Solar Gain * A
300 __ 30 * 10
BTUh _ BTUh /SF
6 ____ hours
1800 _ BTU/day Solar Gain __________________

Loss > Gain

[cem-bsee]

when was the last time you'all went north & saw a sunny day in the northland during Dec ... Mar?
My 1992 NOAA book lists for Erie PA a mean of 6days per month with clear or partially cloudy from Nov thru Apr.

Again, one must have IR rays to get heat by radiation -- including that of the sun.

[Edited by cem-bsee on 12-06-2006 at 07:57 AM]

[sailor27]

Thanks for all the input.
only 2 small partialy blocked windows on south side.
So cover up it is.
God Bless GENE