Radiant heat vs HVAC

**FreakofSnow** · 03-09-2007, 12:02 AM

This summer I'll be slaving away on the new home we will building. I'm trying to narrow down a few last things and one is the heating system. From the 10 or so folks that lived with radiant in their home, all say that is far better than HVAC. I'm pretty much sold on the technology, I'm just wondering if anyone has any other real world experience with it.

I'm considering having it designed by the local plumbing supply shop and running the PEX myself. The final connection to the boiler etc would be made by someone professional. Also, we won't be adding AC, but will have some sort of ventilation/air handler.

I've read that cost differences are 10-25% more than HVAC, sound accurate?
What sort of vent system to use?
Is closed or open system better?

edit: simple 1 story 1600sqft home with about a ~1100 unfinished basement

Don't worry, this won't be the last construction question from me

**InspectorGadget** · 03-09-2007, 12:20 AM

Given the opportunity, I'd go with radiant heat in a heartbeat. It's cleaner - dust wise - and very comfortable on your tootsies. I'd also do a tankless water heater rather than a traditional water heater . . . . to supplement your solar system.

The AGs just installed a tankless system in their casa.

**panchosdad** · 03-09-2007, 08:12 AM

I've put radiant heat into every house I've built of late. The technology is simple, the comfort level is great, and it's at least somewhat more efficient. It also dovetails well with a solar hot water system.

If your house is reasonably sized(<2000sf), well insulated, and well sited for solar gain, you can run the whole heat/hot water system off a simple hot water heater with a solar backup tank. Cheap to install and cheap to run. Depending on your local rates, electric is about as cheap as propane at the moment (For us at .06$/kwh the break even is about $1.60/gal of propane). Run your house off a cheap electric hot water heater and put your heating system budget into solar. That's my plan for my next project.

Have fun, don't stress too much, and take your time as much as possible.

**Froman** · 03-09-2007, 08:18 AM

Go Radiant Heating - the higher upfront cost will be offset quickly due to the higher efficiency of radiant heating.

**danhikeski** · 03-09-2007, 08:35 AM

everyone picked up on some good points, HVAC will allow you to add air conditioning for much cheaper (adding just a condensor) compared to basically having two systems if you have radiant and want AC. but, radiant is easier to run your PEX lines, not having to adjust walls, floors to accommodate the ductwork.

**iceman** · 03-09-2007, 08:40 AM

Radiant heat is great - comfortable and relatively efficient. We considered it when building our house but we live in an area which would be uninhabitable for ~6 months/year without AC, so our costs would have been approximately doubled. We went with a closed-loop geothermal heat pump system instead, which is super efficient, quiet and so far at least has been trouble free. If you don't need AC or can get by with a couple of window units radiant heat can be a great choice.

**trainnvain** · 03-09-2007, 08:47 AM

I have to agree with radiant as well.
Make sure your zones aren't too big and are placed according to how you will be using particular rooms (eg. dont loop your master br with a guest bedroom that rarely gets used).
Oh yeah. Splurge for heated towel racks! Y'know just throwing it out there.

**Grange** · 03-09-2007, 08:48 AM

I had a friend set up his basement floor for radient heat. His biggest issue was designing the tube placement. He said keeping the spacing between the tubes and making sure he had tubing to start and end each tube at the same designated area.

**FreakofSnow** · 03-09-2007, 10:21 AM

I should have mentioned that it will be simple 1 story 1600sqft home with about a ~1100 unfinished basement.

We won't be installing AC, as the area typically does not call for it (see lots of shade late in the day). Also a quick survey of neighbors in the canyon all said they don't have it and don't really need it.

Did you guys do open or closed systems?

Definitely like the idea of using and on-demand water heater if possible.....

**RootSkier** · 03-09-2007, 10:26 AM

Tavis, do radiant, but consider saving money on the tankless water heater and just get a standard one. If you do the pex layout yourself you will probably come out closer to even (you probably wouldn't want to do ductwork yourself, but this brings up the point of an HRV system).

I hope you have taken into account solar gain up there. Southern exposure is pretty good in winter, and if I remember right, there is a big ridge immediately to the west so afternoon summer sun shouldn't be a huge issue.

edit: I have never seen an open loop system.

double edit: www.taunton.com (Fine Homebuilding) has the Breaktime forum, some serious knowledge there. Use it.

**justcuz** · 03-09-2007, 10:31 AM

Radiant is a good way to go. There are some options for you down the road, too, regarding your heat source. My parents just put in an outdoor wood boiler which I would do in a heart beat. The thing burns wood pretty darn slow so if you live in a rural area where wood is relatively inexpensive, this is an option for you down the road.

As far as open vs closed, I think closed is fine as long as you have some sort of filtering system......right? There is a lot of good info here: http://www.wabashremc.com/rebates.html

**Donkey Punch** · 03-09-2007, 10:44 AM

Radiant is great, end of story. Here are some things to make sure of before you start. The company that is designing the system, make sure that they know what they are doing with their loss and gains calculations, there is nothing worse than an improperly designed system. There are a lot of boilers out there spend a little more money to get a good one that is a whole lot quieter and more effecient. Lastly check this website out, it seems that they make a great product and they will send you a small sample and information. I have already sent them plans for the next house I will be building this summer. http://www.warmboard.com/ the increased costs are more than made up for by how fast you can lay everything.

**Tippster** · 03-09-2007, 10:47 AM

I have good old fashioned Hot water radiators, installed when the house was built in 1930. About 20 years ago someone put in duct work for central AC, so we have the best of both worlds. Ceiling fans in all rooms provide for enough circulation to avoid hot/cold spots. I love it.

My folks have a house built ~1870. They installed a High-flow AC system that uses PVC Piping. Much less lost closet space for ducting between the floors and works great.

Our old house was also built around the turn of the century. We didn't need to run ducting between the floors when we installed central AC because we went with a 2 zone system. One was up in the crawl space (too low to be called an attic) that cooled the upstairs. The lower zone we ducted in the ceiling before finishing the basement, so it took care of 2 floors - the main & the basement.

Radiant floors rock, but unless you're building new it's prohibitively expensive to install a saline system. My wife (Remodeler) does install electric radiant flooring (looks like snow fencing) - usually under a new tiled floor. That shit works pretty well, actually, and is surprisingly efficient.

**panchosdad** · 03-09-2007, 11:08 AM

Definetely closed loop. You want glycol in your tubes for better heat transfer and worst case freeze protection. No need for and expensive boiler for your small house.

Warmboard is an ok product, but too expensive for most applications. The time savings you reap on installing tubing is offset by the time you spend making sure all the grooves are in the right place on the Warmboard. If you're installing on blueboard or above a subfloor the tubing won't take more than half a day. If you're snaking between joists it might take a day for two guys. For a main floor installation like yours we'll often put tubing above plywood, then pour a 3" slab over the subfloor. The concrete, stained or dyed, then becomes the finished floor. Great, relatively cheap floor that transfers heat very well.

**goldenboy** · 03-09-2007, 11:16 AM

Radiant is the way. I've noticed that you can get away with a couple degrees cooler setting on the thermostat with radiant b/c it feels warmer.

You said it's one floor, so if you're pouring a slab I hope you're considering staining and glazing the slab to make it a finished floor, which will save a ton of $, and looks good in all the houses I've seen it in.

**FreakofSnow** · 03-09-2007, 11:20 AM

Originally Posted by goldenboy

Radiant is the way. I've noticed that you can get away with a couple degrees cooler setting on the thermostat with radiant b/c it feels warmer.

You said it's one floor, so if you're pouring a slab I hope you're considering staining and glazing the slab to make it a finished floor, which will save a ton of $, and looks good in all the houses I've seen it in.

Snap! Like always, this place serves up some serious information.

In the scenario where you pour a gypcrete (sp?) slab on your first floor (over the floor joists), does that mean increased engineering, bigger joists etc?

**panchosdad** · 03-09-2007, 11:30 AM

In the scenario where you pour a gypcrete (sp?) slab on your first floor (over the floor joists), does that mean increased engineering, bigger joists etc?[/QUOTE]

If you're going to stain/dye a slab you want to use regular concrete, not gypcrete(I think that's the right spelling). It does require bigger joists but it's usually not a big upgrade, assuming your spans aren't too long.

**FreakofSnow** · 03-09-2007, 11:34 AM

Originally Posted by panchosdad

In the scenario where you pour a gypcrete (sp?) slab on your first floor (over the floor joists), does that mean increased engineering, bigger joists etc?

If you're going to stain/dye a slab you want to use regular concrete, not gypcrete(I think that's the right spelling). It does require bigger joists but it's usually not a big upgrade, assuming your spans aren't too long.[/QUOTE]

Gotcha, thats an interesting thought. If anything I might just considering doing it in the basement.

Spans are 28' and less on the the other end (22')

**Arty50** · 03-09-2007, 11:41 AM

As a small aside, others here have mentioned savings by running A/C and heat through one ducting system. This is definitely a way to save money upfront but you pay in the long run. The problem is you have to choose whether the ducting comes through the ceiling or the floor. Remember, hot air rises/cold air falls. Pick the ceiling and you have an efficient A/C system, but poor heating system. Pick the floor and it's just the opposite. If you live in a 2 story house, you can have the best of both worlds. Run the A/C upstairs through ceiling ducts and run heat downstairs through floor ducts or radiant.

Oh and I agree radiant is much better. Especially if you have hard wood or tile floors.

**spindrift** · 03-09-2007, 12:02 PM

A few quick comments (all assuming my knowledge has not become dated):

- Make sure you get a good controller. Radiant behaves very differently than forced air. The more flexible & programmable your controller is the less hassle life will be once you get things set to your satisfaction. If you have tubes in gypcrete or regular concrete you'll have a lot of thermal mass. Expect some slingshotting in the spring and fall. It is the only negative - other than falling behind when a super sudden cold front moves through.

- The tube density needs to be different depending on the type of flooring you will have above it (ie raw concrete vs carpet vs wood)

- Not directly radiant related, but an addition to what some have pointed out regarding gypcrete - you can use gypcrete if you are putting other materials on top (and even that requires doing it "right"). If you leave areas as raw concrete, look into pigmenting it and sealing with a penetrating sealer like 511. This leaves appearance of the concrete unchanged & the coloration is not just superficial. It does not have a surface finish that will ultimately need an expensive refinishing job. It also is not slippery... Also, whether gypcrete or concrete pour - make sure someone qualified (if you are not) makes sure the load bearing is OK

- As others have noted, more zones rather than fewer is goodness

- If you can spring for it, run separate AC ducts now. Relatively cheap insurance in case you want it later. Usable for whole house flush if you need or want it (and if you are building a super tight house, you can even let it bring air in for cooking vents or a fireplace). Plus at that point you can install backup/supplemental heating via a fan, a t-stat, and electric heating coils.

- At least a few years ago there was quite a bit of variation in terms of the kinds of water temps employed. More flow with lower temps is desirable in my opinion.

- Since water heaters are part of the discussion... I'm not sure where things have gone the past few years, but there was a fair bit of dabbling using water tanks with heat exchangers to feed the heat system. Sort of a two-for-one setup. I thoought the idea was interesting...

**panchosdad** · 03-09-2007, 12:08 PM

Gotcha, thats an interesting thought. If anything I might just considering doing it in the basement.

Spans are 28' and less on the the other end (22')

Yeah, it's almost a no brainer for the basement where you're pouring a slab anyway.

You need to keep you spans much shorter, regardless of pouring a slab or not, i.e. you'll need a central beam. Anything much over 16' and you'll end up with a bouncy floor.

**Donkey Punch** · 03-09-2007, 04:20 PM

Originally Posted by panchosdad

Warmboard is an ok product, but too expensive for most applications. The time savings you reap on installing tubing is offset by the time you spend making sure all the grooves are in the right place on the Warmboard. If you're installing on blueboard or above a subfloor the tubing won't take more than half a day. If you're snaking between joists it might take a day for two guys. For a main floor installation like yours we'll often put tubing above plywood, then pour a 3" slab over the subfloor. The concrete, stained or dyed, then becomes the finished floor. Great, relatively cheap floor that transfers heat very well.

Thats exactly how I am doing my dads house right now. I just hate having to put down sleepers for wood, and then laying tile/stone in the other areas over the gypcrete. And in the area that I am building you CAN NOT have just a concrete floor, aparently thats not fancy enough. And the reason I said get spend a little more on a good boiler is the reliability, and the noise levels, there is nothing worse than hearing your boiler everytime it kicks on.

**Pow4Brains** · 03-09-2007, 11:33 PM

Good stuff and just a couple of additions……….
Make sure insulation board (blue board) is used between the ground and slab. The heat is going to move to the most mass and coldest temp. The guy who built my neighbors house did not do this and he is “averaging” $500 per month gas bills cuz the heat is going in to the ground and not the house. He’s fucked now cuz the only way to fix it is to tear out the slab (~2100 sqft).
When running the tubing, always put the hottest water near the coldest temps (i.e. start the supply at an exterior wall or window for each zone).
Gypcrete is good (it adds mass and helps hold the heat better = more effienct), but can break down on weak floors (movement) or in high traffic areas. I have seen this mirror through floor tile. Installing the tubing between the joist space works well if properly installed, but contact with the subfloor is key (lot of staples).
Regarding the vent system, go with seal combustion or “closed”. When the burner for the boiler has to use the air from inside the house for combustion air it pulls the house in to a negative, which creates drafts (same can be said for a water heater too).
You are going to love it!

Originally Posted by panchosdad

Run your house off a cheap electric hot water heater and put your heating system budget into solar.

Be sure to check with your local inspector before doing this. Most jurisdictions will not allow this due to the ASMTA pressure rating of the vessel and the relief valves and safety devices being different (if you are doing this w/out permitting

it may only become an issue when/if you sell). 2nd on the solar being a great addition though.

Originally Posted by panchosdad

You want glycol in your tubes

Glycol can be a good idea, but it does take away some the efficiency and may require up sizing the boiler. In the area you live, do you have to worry about your domestic water piping freezing where it enters the house? If you don’t have any cantilevered sections of the house and it has a basement I wouldn’t worry about it. You could alarm the boiler in the event of a failure if it truly is a concern.

Just my .02

**nick > jesus** · 03-11-2007, 07:50 PM

i stay a friends place in summit county a good bit who has radiant heat, and as nice as it is (especially while tuning skis in the garage) i find it to be kind of dry, though not as bad electric

**FreakofSnow** · 03-25-2007, 01:04 AM

Been reading up a bit more and am just wondering. What are your experiences with staple up systems? Is it a waste of time? Is it still more efficient than HVAC?

I just don't think I can do the gypcrete (too expensive).

The Raupanel looks sweet, but I think that gonna be big $$$$?

And again, the floors will be something of the hardwood/tile/laminate options.