Home>Discussions>INSULATION & HVAC>Choice of heated floor, new windows, or new furnace? Help!!
16 posts / 0 new
Last post
Choice of heated floor, new windows, or new furnace? Help!!

Our 10ft.X 11 ft. dining area is an addition, built over a crawl space, with two exterior walls (facing SE and SW) that are mostly window. This room is always cold in winter, and I feel like it is more from cold air than from a cold floor.

The crawl space has some heat supply, and the exterior walls of the crawl space are insulated on the outside with styrofoam.

The ceiling of this dining area and the 6 inch exterior walls (that are not window) are packed with batt insulation. However the windows are 5 feet tall and almost 21 feet linear width (double-paned sealed, 24 years old if that matters). There are 4 heat registers (2 for each ext. wall) and the area is wide open to the rest of the house.

We have had several furnace people out to look at why the space is so cold in winter... they have all agreed that the 4 heat registers should be sufficient, and that the furnace (5 years old) is powerful enough etc. So I believe the problem is either from the expanse of windows or having a crawl space rather than full basement underneath.

We are now planning to replace the flooring material and would like to fix the heating problem first. We would greatly appreciate advice on where to put our money:

1. should we put in radiant electric floor mats (still keeping the 4 heat registers) or would that mean only the floor would be warmer and the temperature while sitting around the table will still be unpleasant?

2. should we instead replace the windows with triple glazing or whatever is the newest window technology?

3. or should we replace the furnace with a high efficiency one that might blow hotter air into the room? (ps it seems that by the time the air gets to the heat registers in this area, it has already cooled off quite a bit even when we close off the heat in rooms closer to the furnace)(and the basement gets almost unbearably hot from heat radiating through the ductwork nearest the furnace, but ducts are practically cold as they get to the farthest rooms...but furnace people say there is no problem with the design)

I suppose all 3 would be the best but we cannot afford to do more than one... and since the floor is being changed, now is the time if radiant heat is the best solution.

Thank you to all for your suggestions.

MLB Construction
Re: Choice of heated floor, new windows, or new furnace? Help!!

i don't think that radiant floor heating is the solution to your problem. ideally, it would be nice to have closed cell foam insulation installed betewen the floor joists, a backup option would be fiberglass batt insulation. then work on the windows. the difference between windows manufactured 24 years ago and today is vastly different regarding R value. if money is a big deciding factor, which it usually is, i would do fiberglass batts in the floor and get some new "good" windows. then maybe in a year or two you could afford to add in the closed cell insulation in the floor joists.

Re: Choice of heated floor, new windows, or new furnace? Help!!

What MLB said!

I would also wonder about all that glass in one room---if the room is only 10 x 11 that"s 110 sq ft.; except for the amount of glass & the weak heating registers, if the room has insulation like you say, it should be easy to heat this relatively small room; as part of a rudimentary HEAT LOSS CALCULATION you have to multiply the L X W of each window to get the total square footage of all the glass in the room---a lot of heat is going to go right through the glass to the great outdoors on a cold day; the only other factors you haven't mentioned so far are the height of the ceiling (standard is 8') and whether you live in a bitterly cold part of the US or Canada.

I also wonder about the heat output from your forced hot air registers---it sounds like all the heat is being left in the cellar because the main cellar ducts are not insulated & only lukewarm air is getting to the room; the supply/return ducts in the room sound like they also need adjusting/modification---I would call another heating tech & see if he can get a lot more heat coming out of the room registers than what you have now----this should cost a small amount & deliver more heat to the room.

There is also the option of creating a SEPARATE ZONE for the living room heating supply/return registers with the LR having its own thermostat, so that you can control the amount of heat coming into the room, apart from the heat going to the rest of the house; ;if you DO succeed in zoning off the living room for the coming winter , & set the living room T-stat at say 72, you will find out very quickly how long the room heated air will satisfy the T-stat before the furnace has to come on again to replenish the LR warm air---if the T-stat is constantly calling for heat, then the window glass is no doubt the culprit.

If it gets to the point where you have to have the glass replaced with glass that will better hold the heat (better R value), also consider reducing the size of each window in the process, which will also save on heat.

The heating industry uses heat loss calculations (below, rudimentary) to determine how many BTUs (British Thermal Units) of heat per hour it takes to heat up a given room, & how long it takes for the heat to dissipate to the outdoors (depending on outside temp) thru the walls, floor, windows, etc.; warm room air always seeks to escape & move out of the room toward cold air; assuming there is enough warm air being produced by the warm air furnace registers, this warm air will attempt to escape thru the easiest exits---the window glass, any exterior doors, air leaks around windows & doors, a fireplace, uninsulated walls, floor, ceilings, etc.---if there are NO windows (impractical) or doors, uninsulated walls, or fireplaces, any heat introduced into the room will last for many hours.

The basic concept: Is the amount of hot air being produced by the hot air registers sufficient to heat the room; and how long will the room hold the amount of heat produced by the hot air registers so the room feels comfortable----if the warm air being introduced is sufficient, but this warm air very quickly exits the room due to inadequate R factor (heat-holding ability) of the components (walls, doors, windows, etc.), the room is wasting heat & will feel cold.

You would need a heating pro using a sophisticated HLC to determine how much heat output in BTUs/hr is being produced by the hot air registers, & is it enough to meet the heat loss in BTUs/hr of the heated air going thru the windows, floor, walls, etc., which could be 8,000 to 10,000 BTUs/hour; if, for example, the calculated heat loss for the room is 8,000 BTUs/hr, the hot air registers have to be introducing that many BTUs/hr of hot air to keep the room comfortable.

You should be getting SOME radiant heat from the sun thru the SW windows during daytime hours, which should help during those hours; there are insulating-type quilt window treatments that can prevent a lot of heat loss during the overnight hours.


Re: Choice of heated floor, new windows, or new furnace? Help!!

To MLB and von_steuben - Neither my husband nor I are handy at all, so we really appreciate your help! And I don't know how to send individual replies to you so hope you read these.

Yes we are in Canada, so it is pretty cold. Our ceilings are standard, flat 8 feet high.

And for some reason we thought the floor joists under the eating area should NOT be insulated, but instead the crawl space has the styrofoam outside, and I think there were some batts placed on top of the dirt of the crawlspace and then vapor barrier on top of them (I could be wrong but remember something about that). So the crawl space is a bit heated from openings to the fully heated basement, as well as from 'leaks' as heat escapes from the furnace ducts feeding the eating area.

So it will be our first priority to put in Closed Cell Foam Insulation between the joists. Will we have to remove the vapor barrier or the batts sitting on the crawl space floor? (which is about 2-3 feet below joists)? I don't want to have a moisture problem down there...

We love the large windows so shrinking them is not an option. However getting new ones will be second priority.

I believe your advice will have saved us almost $2000 that the heated floor system was going to cost and now we can put that money towards insulating the floor and installing better windows that hopefully WILL do the trick. Thank you so much. This is such a great forum :o

Re: Choice of heated floor, new windows, or new furnace? Help!!

I forgot to mention something important - there are some plumbing lines in the crawlspace, so maybe that's why the insulation was put on the crawlspace floor and the floor joists were not insulated? Will that make a difference for using Closed Cell Foam Insulation?

MLB Construction
Re: Choice of heated floor, new windows, or new furnace? Help!!

won't make a difference at all with the closed cell foam.. they can spray right over the pipes.

Re: Choice of heated floor, new windows, or new furnace? Help!!

Thanks again MLB - so if the plumbing pipes have foam insulation all around them, then will that keep them from freezing even if the crawlspace isn't warm anymore? Or should we keep the heat ducts unfoamed so they can still emit some heat in the crawlspace as they pass through to the heat registers above, and therefore keep the crawlspace and foamed-up pipes from freezing?
I may not understand correctly but am worried if all the joists and the "ceiling" and walls of the crawlspace are foamed, as well as all the pipes and ducts, then the crawlspace itself will be colder than it already is cause almost no heat will transfer into it except from the little access door from the basement to the crawlspace. And then in winter the pipes in that crawlspace might explode...? or maybe i am misunderstanding....

MLB Construction
Re: Choice of heated floor, new windows, or new furnace? Help!!

if all the pipes, ductwork, between the floor joists, etc are properly insulated you shouldn't have a problem. you don't want any hot air duct to be un-insulated. if it is un-insulated then you are not sending warm enough air into the room above. the cold duct work will cool the air on it's way to the room and will not come out as hot as it should be. a good insulation person will be able to wrap everything properly, water pipe and heat ducts, so that there won't be any concern about something freezing.

Re: Choice of heated floor, new windows, or new furnace? Help!!

Many thanks MLB.

Re: Choice of heated floor, new windows, or new furnace? Help!!

I'm going to take a slightly different attack than the other responses. Have you actually had a thermometer in your dining space to see if it actually is cold? It wouldn't surprise me if you feel cold because of heat loss through the glass and small downdrafts off the glass (and even the movement of warm air from the heat registers can cool you off). To give you an example, I'm cold at work, even in summer, and despite our little portable office thermometer being 72/73 the drafts and large single-pane window make it feel cold most of the time.

In other words, you are actually feeling cold rather than being cold. If that's the case, you might be better off replacing the windows or putting some form of radiant heat in (either in the floor at the perimeter or beneath the windows, ugly as that would be) to counteract the feel of being cold. Triple glazing would really help (I've even seen quadruple glazing in Sweden [they've been double glazing since 1600+/- due to wood shortages], it's supposed to eliminate cold drafts off the face of the glass) you in the comfort department.

All that said, insulating the ducts in the crawl space wouldn't hurt as long as it doesn't cool it off enough to freeze the pipes, since windows are a big cost and disruptive. Another option might be simply more insulation on the walls of the crawlspace (I assume your basement is heated) to keep that space warmer and give you a warmer floor.

And most of all, good luck!

Re: Choice of heated floor, new windows, or new furnace? Help!!

Thanks ChicagoCooperator!

You might have a point about air currents especially since the cold is not so noticeable when sitting in the chair furthest from the windows.....We haven't tried a thermometer but maybe we'll do that once the cold weather begins (too soon).

I had a window person take a look yesterday, and he felt the windows were not worth replacing. They are only double glazed, with air in between the glass, but they are hung in a 'fancy' way so that they are cantilevered about 6inches beyond the insulated stud wall to form a wide windowsill inside. He thought triple glazing would add too much weight and possibly make some 'evil' stresses because of the cantilever, so even if it helped solve the problem, it could create new, worse issues.

He did suggest that the outer 3 or 4 inches beyond the stud wall to the glazing is probably uninsulated. So each window is like a box projecting from the house exterior wall, and that box itself is not insulated except whatever R value you get from 3 inches of wood. (hope I am explaining clearly). Which I suppose is very bad and maybe not repairable.

So I guess we should thicken the insulation in the crawl space exterior walls, and make sure it is on the inside of the concrete too and not just on the outside. Then insulate the heating ducts if possible so the air that comes out of the heat registers is a bit warmer. But still let some warm air heat the crawl space so the plumbing lines don't freeze.

As for radiant heat, is that the same as electric floor mats that would go underneath the new floor surface? That was my first idea to fix the heating issue but I didn't realize that the heat from the floor would only rise a few inches. But maybe we should do the crawlspace insulating plus the radiant heat since the windows might not be fixable. If you meant something else by 'radiant heat' please let me know...

Thank you all for your input....feel free to keep adding ideas, I really appreciate it.


Sponsored Stories

TV Listings

Find TV listings for This Old House and Ask This Old House in your area.