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Radiant Heat question

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Joined: Dec 21 2006

Brrrr, is it supposed to take hours to heat up the house? We have concrete floors, and when I got up this morning it was 57 degrees, two hours later its 59!

Is this normal or is our heater not functioning up to par? Our gas bill last month was outrageous.
thanks in advance!

Joined: Mar 21 2003

Usually we expect the house to be fairly comfortable within two hours of turning on the heat. The concrete slab is a huge heat reservoir and it does take time for it to heat up.

However there are a number of things that can make the answer vary dramatically from house to house. For example, how good is the insulation between the living area and the outside? This not only includes if insulation has been added to the roof and/or walls but what kind of coverings you have on those big floor to ceiling single pane windows.

Another one is how much insulation do you have between your radiant heat and you? If you have wall to wall carpets you are keeping the heat out of the living area. With wall to wall carpets and no window coverings your original boiler, even if in perfect condition, may not be able to keep up on the cold nights.

In our small courtyard model Eichler the original 1958 AO Smith was able to keep the house comfortable during the last few days when the outside temperature dropped to 29 (as recorded on our outside thermometer). We have foam insulation on our roof and don't have carpet in the public areas. Also some walls have had the insulation upgraded.

I expect our gas bill to quite high for this month as the boiler has been running overtime. If/when the original boiler fails it will be worth getting a high efficiency replacement. We may end up replacing the boiler early even though crunching the numbers tells me it is not cost effective to replace a working boiler. The biggest portion of our CO2 footprint is our natural gas heating which makes it a good place to focus environmental efforts.

Joined: Dec 21 2006

Thanks for info. I have no idea as to the insulation between the walls, we do have a foam roof and no carpet. We have a very thin layer of poured concrete on top of the slab, so I don't think we can get any closer to the radient pipes.

I have no window coverings, mainly because I like the look, I had the sunchek put on over the summer and it keeps the house cool. Guess I'll have to look into some kind of blinds, any suggestions? This is our first winter in this home.


Joined: Sep 16 2005

When I first move into my Eichler I was told it take approx. 4 hours to heat up. I would say that it just about correct. I have the heater on a timer/thermostat that really helps. The few windows that I covered, I went with the honey comb blinds. They are in the bedrooms and office off the atrium. The honey comb really helps keep the cold out.
Good luck,

Joined: Mar 16 2005

Yes, in my 1973 model (AO Smith & copper), it takes hours to heat up 2 degrees -- one owner said the boiler ran 8 hours to get it back up to the high 60's after leaving it off for vacation.
(1) Supposely, the floor should be about 85 degrees after the slab is fully heated and there is heat convection to room air - - I seldom got the "toasty feet" feel that radiant heat advocates like because my floor (75%) is 18-inch Italian tile; the Pergo areas are better for toasty feet.
(2) My boiler will run about 135 hours this December (using the thermostat's counter) and that's with an out-of-town vacation. Everyone's circumstances will be different (stay-at-home during day, temp settings, etc.), but the lack of wall insulation & insulated glass and slab foundation make Eichler's very costly to heat, and the radiant heat very slow to respond although it is a soft & comfortable heat.
(3) In an addition, I use a AC/Heat mini-split and it can heat up 5-10 degrees (room air) in about 30-45 minutes, but the tile floor would still be cold as ice.

Joined: Dec 27 2006

I was told that a floating floor was not a good option for a floor with radiant heat, so we are looking to order travertine. Should we change our minds? I'd like a warm floor...

Joined: Mar 25 2003

Two hours isn't long enough from an off position and you don't mention if the house ever gets warm enough. If not, something's wrong since having bare concrete is the best way to ensure you are getting the most from the radiant.

Have your boiler checked out and cleaned. Or replaced if necessary. The new boilers are much more efficient. Get a couple estimates as I've heard folks say they've paid as little as $4-$5k to as much as $11k. The lower end of this range seems more typical.

Get a programmable thermostat. It's much harder for the system to go from off to warm and toasty than it is to raise the temperature a few degrees. Set the system to kick on about four hours before you get up and don't set the low night temp more than 5 degrees away from the high temp and you should be comfortable with only moderately horrible gas bills.

PS: some folks advocate leaving the thermostat at 68 degrees at all times so the system never has to work overtime to get the house warm. I believe this will probably be a little more cost effective, but 68 degrees isn't warm enough for me.

Joined: Apr 10 2006

This is my first winter in my Eichler as well. Mine takes approx. 2-3 hours to raise about 2 degrees. I have a programmable thermostat that is set at 65 during the day and between 67 and 69 at night. So far it seems to work out okay (that is except for the the gas bill!)

Joined: Mar 25 2006

Most radiant systems are designed these days to be able to raise temp 10 deg in an hour. That's a little much to hope for in an Eichler (lot of factors), but wall to wall carpeting and a 30 yr old boiler will pretty much kill you. Throw in a an old tired maybe unersized pump. You forgot to mention the btu input of the boiler. It's time for a new high efficiency boiler that's properly sized. Jerry

Joined: Dec 21 2006

Jerry, we have a concrete floor, and a new hi efficiency boiler that ranges from 20,000 to 185,000 BTU. We've had suncheck put on all of the windows and double cell honeycomb blinds. Aside from replacing the windows with double pane and insulating the walls, it feels like we've done quite a bit to keep this place warm in the winter. Perhaps its time to get PG&E out, although we recently purchased the house and it passed all of the inspections.

I'm thinking that eichlers are just expensive to heat.

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