kevins_news wrote:

On Mon, 26 Jan 2004 19:07:34 GMT, kevins_news
wrote:

I know that question is too open ended to really answer. Each house
will behave different. Each room will behave different depending on
windows, exterior walls, etc. But I'm just looking for some sort of
estimate.

Say it's -15C outside and +20C inside at midnight. If i left the
furnace off (gas forced air) all night, what kind of temperature could
be expected at 8am? I guess a "If it drops lower than X then you may
have issues" is the kind of answer i'm looking for.

The reason i ask is because i'm an insanely over-critical person who
wants to squeeze every bit of efficiency out of this house until the
next one which i will have built properly. :-)

I'm in the middle unit of a 3 unit townhouse. So i share a wall with
each nieghbour on the sides and only my front/back walls are exposed
to the elements. However I have a 2nd story which neither of my
neighbours do, so upstairs is exposed on all four sides. Because the
vast majority of my main floor walls are shared with neighbours i
figured that my heat loss should be significantly better than any
detached house. But i have nothing to compare against. Buit new in
2001 according to ontario building code. I think that's r-34 in the
attic and only r18 in the walls. All the windows are double paned. I
can't feel any air leakage and no condensation or ice ever forms
between panes but the bedroom windows ice up like hell every night
along the bottom edge. (35% humidity inside at 19C with -15C outside).

I haven't done any tests to see how quickly the temperature drops but
i was just looking for some sort of general numbers to compare against
once i do.

any thoughts appreciated.

One more comment. 1700 sq feet plus basement is the size.

You are right it is impossible to answer with any degree of
accuracy. But a few questions, the wall are ONLY R18?
Second, why don't you just turn the furnace off and see how
far it drops? Third, why do you care? And none of those
are smart-ass comments. I don't understand you point. Turn
off the furnance and you find out. Anything below about 60
F (? 14 C?) would be too low for efficiency in reheating, so
you just set your thermostat for 60 F for efficiency.
Personally, I don't want my house going below 65 F even to
say a little money.

Finally, even in my 1500 square foot ranch which is fully
exposed and the walls are only R-11 insulated, the temp
would not drop much below 60 F overnight with those outside
temperatures. I would suspect that your house would not
drop from 20 C to less than 14 C overnight unless you had a
real strong wind blowing.