Radiant Heat with GSHP...Yea or Nay?

[MGH PA]

I'm looking for some ways to trim down our costs for building our new home. There are certain areas where I feel must be priortized, including insulation and HVAC. Our plan is to go with a three well GSHP at ~$28k before tax credits. We're doing an ICF basement, but just plain 2x6 NuWool on the second floor. We originally had specified radiant heat in the basement as well. Our builder is including this as a $10k allowance which seemed a little high. I swore I wanted the radiant since it will be living space (rec room, guest bed/bath, gym, etc.), but then I thought maybe it would be best to simply invest more in sub slab insulation and call it a day.

I know there are differing opinions on this, but I feel as though the basement being dry, and well insulated will negate the need for the radiant heating and the GSHP should suffice even at the lower level.

Any insights are appreciated because this is definitely a decision that there's no going back on once the slab is poured, so I want to make sure I do my due diligence on this.

Thanks.

 

[Lelandwelds]

I don't live in a cold weather state but pretty few ground source heat pumps are installed correctly. Fewer still have a reasonably short payback. Seems risky.

Radiant floors are wonderful though for background heating. That warm foot thing is pretty awesome.

 

[MGH PA]

I don't live in a cold weather state but pretty few ground source heat pumps are installed correctly. Fewer still have a reasonably short payback. Seems risky.

Radiant floors are wonderful though for background heating. That warm foot thing is pretty awesome.

Plenty of homes built that have them around here, and several friends that have them. They're incredible. I do agree on the payback period. The 30% tax credit helps a bit in that regard.

 

[dadster4]

I don't know squat about GSHP systems but I have installed many radiant systems. At the very least, install 1/2" oxygen barrier PEX (12" O.C.), over foil face bubble-wrap type insulation, over the 2" sub slab insulating foam board. With the tubing installed, you can tie it in to any heat source in the future, nothing beats the comfort of a heated slab.

 

[oosik]

My folks built a ranch style house with radiant heat in the concrete slab. Local contractors though my dad was crazy. They had no experience with that type heating system. Folks would "drop by" in the winter just so they could remove their shoes and walk around on the cement floors in their stocking feet.

As I remember - my dad did research on in-slab radiant heating systems for a couple years prior to the house being built. I also remember the miles of copper pipe and how careful they had to be to ensure the copper piping was just at the correct height when the concrete was poured.

 

[techman]

I installed a couple of GS radiant systems some years ago. Unfortunately is is more complicated than conventional GS systems. I used ClimateMaster GSW water-water GS heat pumps. To prevent short cycling I installed 2 40 gallon hot water heaters as hot water (domestic heating) storage tanks. The electric elements were connected and available for emergency/backup heat (never needed backup as far as I know). A circulator with outdoor reset aquastat controlled the heat pump to maintain heated water in the tanks. Zone circulators handled the radiant loops. To be properly designed, the radiant tubing installation must be configured for 120 deg max water temps, due to the available water temps from the GS units.

Cooling required using an air handler designed for chilled water. Motorized zone valves were used to divert flow between the hot water tanks (winter) and the water air handler (summer). A separate circulator was used for the chilled water path. A small PLC was used to perform the logic of switching modes, controlling which circulators to use, etc. It could have been done with relays, but the PLC was cheap, flexible and reliable.

The systems worked well. The only issue was during season change where AC during the day and heat at night was needed. It initially takes several hours to heat the tanks, so a short call for heat might end up with hot water that is not used, a small loss of efficiency. There is a unit I have seen that offers an evaporator-blower for AC and hot water loop for heating, but I do not remember what brand offers them.

paul

 

[NorTracNY]

I did radiant in the house when built and I love it. It's good that you're thinking about all of this now, as it all becomes cost prohibitive later. My folks then built their place and put it in the house and walk out basement. What direction do you have windows in the basement? Remember that it's a big thermal mass and passive solar principles are probably much better to think about. If you want to walk around barefoot in the basement, go with the radiant heat there. Otherwise just put in the insulation. My folks place has only South and East facing windows. I don't believe the radiant heat operates much in the basement. I do not have a walk out basement and therefore very few windows allow the sun's heat in. It's comfortable in my basement in the winter, but I always have something on my feet.

 

[fishheadbob]

Yea !
I've had a GSHP for 4 incident free years. I cannot accurately say how long or short a payback period is involved as I heated primarily with wood for 35 years burning about 20 face cords of hickory per year. Taking this wood from standing tree through ashes was a lot of work, and I also burned about 200 gallons of oil when away or fed up with feeding the furnace. Money went to chiropractors as well. I am 70;I have killed enough trees.

Here is what I can say. I live in a 1830's 2100 square foot farmhouse built to the exacting building codes in effect in 1835, also known as none. I had a hefty propane bill , $40 per month average, exclusively for hot water as my supplier charged me up the wazoo for small deliveries even though I had a 100 gallon tank. Natural gas isn't available, that would have made a cost analysis interesting as hydrofracking, love it or hate it, has clobbered the price of natural gas. My geothermal system includes hot water and central air. My electric bill has risen since I run pumps and blowers most of the time, but my electric bill hasn't risen by the $40 per month those stinkers at the propane company were charging. I keep my house a few degrees warmer in the winter, and at 74 in summer.

My advice would be to thoroughly research the companies doing the gshp work. There are 2 big ones in my area (Buffalo) which have done hundreds of installations. I checked their ratings online, with the BBB, and I checked with folks who had used one company or the other. Both companies had glowing reviews.
I also found a few companies advertising that they did geothermal systems, well actually they always wanted to do one. I felt it best if they learned their craft on someone else. Both companies I worked with used WaterFurnace brand systems; I don't know if WaterFurnace is better than others or if they were offering companies the best deals. One of my 2 competing companies was big on the 3 well approach, the other was using about 1/4 acre for an underground loop field. Both companies bids were almost identical around $25,000, both companies knew I was seeking bids from their competitor,and I finally got one down to $24,000. I am happy as a clam with my system, but again you really have to do your homework before spending that kind of dough.

 

[Rustyiron]

I know there are differing opinions on this, but I feel as though the basement being dry, and well insulated will negate the need for the radiant heating and the GSHP should suffice even at the lower level.

Any insights are appreciated because this is definitely a decision that there's no going back on once the slab is poured, so I want to make sure I do my due diligence on this.

Thanks.

I'd like to direct you to another forum.GreenBuildingTalk - Green Building Forums on Insulating Concrete Forms (ICF), Structural Insulated Panels (SIP), Radiant Heating, Geothermal Heat Pumps, Solar Power, Green Construction Projects join and ask a lot of questions. Many there are in the business but are not selling you anything.
I'm living in my first radiant (wood gassification fired) home, I did a lot of reading & homework about insulation, radiant and other smart building things that get overlooked by many builders. I lucked out finding a great radiant design guy that was super into his work. If your as lucky your GSHP "guy" can guide you through this in the smartest way possible for your requirements, not just the best sales & installation deal for him. Same go's for your insulation contractor. The biggest overlooked item I see in the "pitch" you get from them is they mostly concentrate on "R" values & fiberglass. AIR INFILTRATION and moisture control is #1 concern. Every penny spent on insulation is one that's eventually NOT spent on whatever you use to heat & cool, for the rest of time.:thumbsup:

 

[Raspy]

The basement is the most important place to have radiant heating, and especially in your case where you are planning to use that area. It will carry the majority of the heat load for the rest of the house and make your basement a place you want to be, instead of a place you'll always regret not heating. Don't kid yourself into thinking it's not important.

At least get the tubing in and have it ready to go regardless of your heat source. About $600. worth of tubing will heat about 700 sq ft of floor. Two people can tie down about a 1,000 sq ft of tubing in a day. Then add a manifold system for $400. to $600. and you are getting pretty close to your rough-in cost. Set your rebar on 12" centers in both directions. Run the PEX on 12" centers with a 6" on center strip around the perimeter and 6 or 9 inches in the bathroom. I don't know the size of the area in question, but these numbers will allow you to do the math.

Personally, and this is just me, I would never do ground heat.

Once you've made the commitment to do it somewhere, you can then tap into the same system to do the bathroom floors in the rest of the house, and/or the kitchen, etc. Or just do the whole house and forget the scorched air nonsense.