I’m in the process of installing radiant floor heat in the addition I’m building on my home. A few questions have come up which I would like to get some input. To start here’s some information. We are adding approximately 700 square feet (one third of that is on slab). We are in the north east just north of New York City. The additional is typical cedar siding construction.
My questions: The ½â€ PEX tubing is going into the bays under the sub-floor. I understand that the heat response time is slower when using this method. Is it significantly slower? The finished wood floor will have an intricate pattern. I would prefer not to remove the finished floor if there ever was a leak.
My next questions, my plumber has recommended a Weil McClain CG-4 boiler and Plus 80 water heater. Is this considered to be a good system or should I look at other boilers.
Thanks for your help.
Jay
Replies
The response time of all infloor/underfloor systems will be slow compared to forced air or basebaord/radiator hydronic or steam heat. Is the method you describe significantly slower than any other (all other things being equal)? No.
Is a W-M GC-4 and a Plus 80 indirect water heater suitable for heating a 700 sf addition? If this equipment is to be used only to heat this addition, I would have to disagree with the selection. If this is to replace an existing water heater AND provide heat for the addition, I would only suggest that you use a smaller water heater, unless you need the equivalent of 100 gallon commercial water heater in your home.
A better selection would be something like a Bradford-White model M-1-XR65T6BN.
Response time only matters if you change the temperature setting a lot, such as with an infrequently used space or a vacation home. Not much of an issue for a regularly occupied space. A well-designed system should be operating on outdoor reset, so the floor temperature should always be a good match for the heatloss of the space.
Look into http://www.htproducts.com
They make modulating/condensing boilers which have dynamically adjustable output temperatures. Ideal for low temp or outdoor reset applications combined with domestic hot water production.
Its very, very important to distinguish between thermal performance and thermal lag…
Radiant transfer (performance) is instantaneous – like turning on a light…as soon as there is a temperature difference between two surfaces there is immediate transfer of Btu’s via radiation. Btu’s don’t have to think about moving from hot to cold…its automatic and instant.
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The time to get a building up to temperature is the delay (thermal lag) – and is a functions of the building efficiency and the type of radiant panel.
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Did I mention how important it is to not confuse the differences between thermal performance and thermal lag?RBean
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