I'm planning to build a new home in Northern Utah and had some questions on radiant heat that hopefully someone can help me with.  We're early on in the deisng process so the questions are quite general.  The home will be ~4000 square feet in a basement +2 design with ICF essentially everywhere possible.  I like the idea of radiant heat, but am wondering where it would be worth it to install in such a home.  Is radiant heat worth doing in the entire house?  Can that eliminate the need for forced air heating all together (i'd still plan on an AC unit and HRV for the home)?  Is it more cost effective to do only certain portions of the house with radiant heat?  In reading through some of the forum topics, I've seen many of the benefits of radiant heat, but what are the drawbacks?

I appreciate any suggestions or info anyone can provide.

JPWhite

JP,
Your question can you heat entirely with radiant, yes, no problem especially an ICF design, you may have some need for supplemental radiators if there are great rooms with loaded glass walls and cathedral ceilings, but generally speaking yes all radiant in floor can be done and is very comfortable and fuel efficient.
The cooling HRVs system you mention can also co-function with the boiler and a supplemental heating coil can be added to provide additional heat as needed through the forced air side of the home.
We design these types of systems regularly.
Dan

Posted By Blueridgecompany.com on 09 Jun 2010 12:47 PM
JP,
Your question can you heat entirely with radiant, yes, no problem especially an ICF design, you may have some need for supplemental radiators if there are great rooms with loaded glass walls and cathedral ceilings, but generally speaking yes all radiant in floor can be done and is very comfortable and fuel efficient.
The cooling HRVs system you mention can also co-function with the boiler and a supplemental heating coil can be added to provide additional heat as needed through the forced air side of the home.
We design these types of systems regularly.
Dan

Thanks for the reply Dan.  I don't anticipate massive cathedral ceilings or window walls.  The supplemental heating coil sounds like a good idea as well.

Is doing whole home radiant heating worth the cost?  Does having carpeted bedrooms and great rooms defeat much of what the radiant heating provides? Are the heating lag times more of an annoyance than what they are worth in spring and fall?  I've never had any experience with this type of heating so I really don't know the pros and cons as someone who has lived with one would.

JPWhite

as with most things, what you get can vary. a well designed and controlled system will simply provide excellent comfort and efficiency throughout the heating season, period.

If your heat load is very, very low, then something like panel radiators or what have you might make more sense.

"worth the cost" is a tough one though. depends on what you mean. Will it save back the additional cost of the install? maybe not. its efficiency will have savings, assuming it's not hacked together, compared to forced air heat. it will be more comfortable... probably a lot more in most cases. how much that is worth, of course depends on the person.

Radiant will always cost more than forced air.
You are building a sizable home, the net cost for the mechanical system is a small compared to comfort and resale value added.
I would never consider building a home with out radiant floor heat. It is just to nice.
It is not to difficult to accomplish as an owned builder or providing your contractor with a system to install. Our designs can vary from complex to straight forward.
Lag time is not a big issue, this to can be balanced with a hot air coil for quick response and also surplus heat.
So I am bias to in floor heat.
Dan

there is almost never a need for a forced air coil. a decent control system is all most people need.

and I loved infloor too. but there are times that it is a marginal improvement. hydronic in general though is almost always by far the best choice for comfort and efficiency.

Radiant floor heating is a luxury.

Most of the new systems radiant floor heating systems here in chilly Minnesota are installed in walk-out basements, while the upper levels are handled with a traditional forced air unit which includes integrated heat, AC, humidification, air filtration; this primarily done because this combination is half the price of a full house radiant system.

AC and heating are not related duties, so the best comfort systems (rare in residential) place tube in the floor, ducts in the ceiling and result in perfect comfort.

It is unfortunate that so many here in Minnesota compromise heating comfort for a few weeks of cooling, but builders can't find a margin in high tech expensive radiant technology. This is especially true when you get out of the relatively cheap slab basement and try to radiate upper floors where material and labor go up dramatically.

Where houses are built slab-on-grade and most especially in drier climates radiant floor goes in without question. It is the smart decision where comfort, efficiency and longevity are the main goals.

I read this thread this morning and i wanted to comment that I'm thinking of doing exactly the following!

BadgerBoilerMN
"Most of the new systems radiant floor heating systems here in chilly Minnesota are installed in walk-out basements, while the upper levels are handled with a traditional forced air unit which includes integrated heat, AC, humidification, air filtration; this primarily done because this combination is half the price of a full house radiant system."

It's not the cost of the first floor radiant heat, it is the cooling that is needed for POSSIBLY only a few weeks, usually 8 to 10 weeks that the AC is on. Cost is always a factor but I put comfort first. Since I'm probably not going to turn on the radiant heat on in the basement (a walkout) and hopefully use solar panels to heat the floor in the future!

Now all I have to do is have the floor plans finalized and get quotes on a radiant floor of approximately 1200 square feet!

John

Thanks all for the information.

So what prices would I be looking at for a 4000 sf, basement +2, 5 bedroom whole house radiant heat versus just the basement radiant and forced in the +2?  Is there a quick way to get in the ballpark with an estimate for both methods?

JPWhite

Prices depend on the market you are in, products, features and the quality and experience of your contractor. Shop around and ask about a heat load analysis. Most will hem and haw; makes for a short list.

You WILL turn the basement on if you spend any time there; and why not, it will cost a few dollars a day for perfect comfort.

costs could be anywhere from 4 to 12 per sq ft depending.Budget aside if I were designing the system it would include radiant in all areas with gypcrete or mud bed on all floors that are not concrete. Zonning as needed, a tekmar integrated control system, low mass condensing boiler with indirect water heater[ or a geothermal heat pump], and garage and basement radiant. Add in a well insulated foundation and slab and follow up with a Variable speed air handler with zonning and sealed duct work.
It all starts with manual J load calculation.properly designed piping, controls , duct work , pumps ...etc..etc....A system like this would cost 10 to 15 per sq ft depending on local codes and labor costs... add for HRV, elctronic air cleaner UV light Humidifier and I would highly recomend looking into Geothermal. Eric

Eric,

You mention "gypcrete or mud bed on all floors that are not concrete." Pardon the uneducated question, but does that mean no carpet anywhere in the home? I've seen a range of opinions as to how well radiant heating works under carpet and was curious if that was driving your statement at all. Any ideas on the cost of a traditional heating system would cost? I understand it will vary by area, but the relative cost will be useful information to have. Thanks for your input.

JPWhite

gyp would be the radiant medium and finish floor would go over that, including carpet. carpet is not often a great choice over radiant as it will at the very least raise your system water temp requirements which reduces efficiency. but slab rubber pads and thinner, synthetic fiber carpets can work decently well.

JP,
Sound and fire along with thermal mass are reasons for gypcrete.
I agree with Robs comments on carpet.
As far as traditional costs I would say 4 to 7 per sq ft. depending on labor costs, competition, local codes, quality of workmanship etc..
If you decide to go gfa make sure the system is designed properly. Again manual J for heat cool loads and D for duct design. I would look look at VS 2 stage furnace with zone controls and HRV, EAC. humidifier. Make sure they seal the ducts with mastic not silicone caulk. Eric

Just found this link...I too am going to be building new in Northern Utah, elev. 5000'.. 1600-1800 sq.ft, 200' loft, partial walk-out basement, southerly exposure.  I'm interested in a solar hot water/ radiant heat system with possibly propane/ elec. backup for cloudy and abnormally cold days.  Am I asking for something that wiull be extremely cost prohibitive and for a primary backup, am I better off with elec. or propane? I'm in the design stage and would like to get some feedbackon this.  Thanks...geonutts

I would use high mass in the form of 5000+ gallons of water and an air to water heat pump.

you are unlikely to do primary heat with solar. solar assist, maybe, but heat pump w/PV and "net metering" is far easier than solar hot water trying to produce the BTUs you need in january.

Unlike retrofits, on a new build you have options max out the R values and optimize the passive solar design to make the bulk of sunny days primarily-solar.

Propane (even condensing propane) is a fairly expensive way to heat, as is resistance-electricity. Highest efficiency heat pumps aren't cheap up front, and neither are photovolataics (PV) except where heavily subsidized, but that's still how it's done on many Net Zero Energy homes where the costs/benefits have been well analyzed.

To optimize cost/benefit of building upgrades on a new home (or even a retrofit), it's worth using tools like (DOE freeware) BeOpt to model the home at it's site & orientation to determine where & weather higher-R is better than lower-U windows, etc. It's not exactly a passive solar design tool, but it can help rough in passive solar designs. See. http://beopt.nrel.gov/

Air to water heat pumps are quite pricey compared to ductless air-to-air, but that would be the way to get the extra cush-factor of warm floors. OTOH spending the money on a higher-performance building envelope (instead of hydronic heat pumps and radiant floors) could make your heat loads low enough that radiant floors don't really add much to the comfort factor they way they do on homes with more conventional heat loads. If you only have 5BTU per square foot heat load at the outside design temp, during the average wintertime conditions the floor never gets more than a degree or so above room temp. In a high-R home point-source heating works pretty well, and single-head mini-splits are pretty cheap but highly efficient heating & cooling "systems" well suited to a UT climate. With better class ductless air-to-air you'd use about 1/3 the power in "backup" mode than you would with electric resistance heating, and you would have highest efficiency air conditioning as well.

Even if you don't install it initially, designing the roof pitches for optimizing PV is worthwhile, since even without subsidy the costs will eventually come down to the point that it's worthwhile to invest there. (Where subsidized heavily that day is already here.)

you don't need radiant floor to use load water heat pumps. radiators, radiant walls, or low cost fancoils can all be used as well.

minisplits are cheaper until you add a few units it seems. depends on the floorplan which would win.

At a high enough R, low enough-U, it doesn't much matter what the floor plan is- room to room balancing can be tweaked by the ventilation air. At a low enough loads adding complexity to the HVAC only adds cost, not comfort, not efficiency.

Design temps for this place is likely to be about +5F (Provo at ~4500' has a design temp of +6F), which is the design temp for Worcester, MA, where I've been advising on (but not contracted to) a deep energy retrofit, in a low-mass 3-family building with significant shading factors limiting passive solar options. With R40 whole-wall R and U0.18 windows and good air tightness (final test not yet in) each of the three units is being heated with a single-head mini-split, and the doored-off rooms are temperature balanced via the direction of the ventilation air. (I did not design it- I only reviewed it, but it pencils-out.) Manual-J on the lossiest unit is about 11KBTU/Hr @ +5F, and it's being heated & cooled with a 1.5 ton mini-split.

Had it been a 3-floor single-family they would have gone with a 2.5 or 3-ton 3-head multi-split, zoning by floor, but since the tenants pay the heat, using 3 minisplits was deemed the cheapest & way to have it separately metered. Total installed cost for the three was under $13K. A multi-split solution would have been under $10K. The ERV ventilation systems came in under $4K per unit, ductwork included.

On a new building in a sunnier climate & location, a high-R passive solar design with some interior thermal mass could take the peak output requirements down even if it needed to be somewhat lossier for passive-gain on some of the windows. Getting a ~2000 house to mini-split/multisplit heat load levels doing some temperature balancing with the ventilation air should be possible without taking it to the PassiveHouse extremes the way this guy just a bit down the road from me did:

http://www.beatonconstruction.com/passive-house/

He's heating (but mostly cooling) this ~3400' place with a 2.5 ton 2-head Mitsubishi, which is (like many aspects of this house) is a bit overkill. But with 2 heads it allows the upper and lower floors (but not individual rooms) to be zoned separately. There are a very few high-efficiency 2-head multi-splits out there with lower output than 2.5 tons, but I'm not sure what was available the day they signed the contract. With inverter drive ductless some amount of oversizing helps (rather than hurts) efficiency, so if anything the oversizing boosted both low-temp capacity as well as efficiency. (Word is they're having to run it in cooling mode a lot even in winter- their kids run too many big-screen TVs tied to gaming systems, and they have more plug-load than heating-load much of the time!)

The outside design temp between Beaton's PassiveHouse and the new construction in N. UT may be similar, but the outdoor humidity in southern New England is much higher, cutting into output near the design temp. A moderately massive house with good solar gain in a drier winter climate should be able to coast comfortably through the comparatively rare instances where defrost time is eating too heavily into the heating duty cycle of a mini-split for it to actually keep up.

There are many ways to slice up the construction budget & efficiency apple, which is why tweaking it in tools like BeOpt is useful. But there's some elegance to having a sufficiently low load that cheap point source heating can be employed without risking chilly or hot rooms.