RFH vs. Hydroair vs. Baseboards - Help!

rickgreg

A few weeks ago, some of you recommended Hydroair as a good option for adding AC and heat to the 650 sq ft addition we are planning. Since then, I met with my builder's recommended HVAC contractor, and the discussion raised a few more questions. I'm hoping you experts can shed some light!

By way of background, the house is in central CT. The project involves adding a 2nd floor to part of the house. Approx 3/4 of the new space is over an unheated attached garage. Existing heat is hot water baseboards. Current house is on a single AC zone, system around 7 years old.

Here's where we are:

Hydroair: This seemed like a nice choice... but the air handler will have to be in the attic (unheated) and will require antifreeze. Downsides include reduced heating efficiency due to antifreeze, but the real concern to me is the future maintenance required to maintain the antifreeze (he is suggesting glycol). Not sure I want to put my heating system at risk and create new maintenance costs and headaches. Also, forced air heat over an unheated garage raises comfort questions for me.

RFH: We are already pushing our construction budget... so I hadn't really considered RFH seriously. Then the contractor suggested a cost effective way of doing RFH is doing a suspended system in the joist bays. He says Wirsbo can design an installation that will work well. Any concerns about this kind of install? Floor will be plywood subfloor plus carpet. I like the idea of radiant over a cold garage for comfort...

Also, what is the real deal on heating efficiency with RFH? I've read it is more energy efficient, but also that it is not practical to set-back the temp at night, etc because of mass-heating ramp time.

Finally, the fallback is baseboards, which we have now and live with fine. Only real concern here is furniture placement, which we could manage.

(Obviously the RFH and Baseboard approaches would involve a separate AC only system)

I know I've tossed a book full of questions. Any insight is appreciated!

-RG

jerry scharf_3

Another option

Rick,

Like you need another option. Since you have baseboard already running, you have the right water temperature for either more baseboard or for panel radiators. I would seriously consider the panel rads with TRVs for the addition. You will get great comfort and the minimum impact to the budget.

I am not a fan (sorry...) of forced air heating combined with A/C. For A/C you want the supply and returns as high as possible. For heat you want the opposite. Always a compromise and you end up having at least one be much less comfortable and efficient than it would be as a separate.

Depending on the type of boiler in use, radiant can be much more efficient. With condensing boilers and a radiant only system, the return temperatures are often very low and that makes for very efficient systems. Some reports are in the 98+% range for the boiler. Given that you have the baseboard in place, you would use a mix-down setup (something like a Taco RMB) and thus the savings are not nearly so great.

Given the unheated garage underneath, you will have to insulate the hell out of that space for floor radiant. The hotter the air under the floor, the greater the wasted heat will be. So that suspended tube design the contractor is offering you requires the hottest water and would have the most heat loss to the garage below.

jerry

Joe Brix

raidant flooring

I assume the tubing could be put over your exsisting flooring with a product like warmboard, keeping the tubing away from the unconditioned garage. But it will cost money.
Anyone look into putting the air handler in the garage and blow up? I doubt the garage gets below freezing if it's attached. You could also use a heat exchanger to isolate the glycol loop for the attic from the rest of the heating system. As Jerry said, I doubt it would cost to much to add baseboard if you can pipe it around by going down into the garage. Just insulate the pipes.

Unknown

BBD

Put in the baseboard and nice carpet. The carpet will keep the cold from the garage away. (BTW - you can also put in a freeze stat on the air handler instead of glycol in the system)

Or how about Vasco Steel Radiators? Less room on the walls, more BTU. Stay with the Lotus and you wil save some money, be able to get them more readily and they look good.

Just my 2 cents.

Unknown

you will have low mass, so that problem with setback is eliminated using RFH, however setback with ALL forms of heat on a nightly basis is a little counter productive. The mass of the room and everything in it cools down, and even if air temp is satisfied, it takes time to heat it all up again so that you are truly comfortable. This is because of the "Mean Radiant Temperature" of the room; if the objects are cool, you lose heat to them and feel chillier.

In short, night time setback is really kind of a waste unless you have a space that you really want warmer in the day and cooler at night. Bedrooms, for instance, you usually want cooler at night... unless you really want them warmer during the day though, zone them seperately and just keep them cooler, and keep the rest of the house as warm as you want it, consistently.

The application you are looking at for radiant will not be much more efficient than baseboard, however, it will be a high temp system unless plates are used, and plates will increase the cost. Since you have a carpeted floor anyway, I would either do ceiling radiant (which can be pretty cheap) or stick with baseboard.

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