Topless heating – Can radiant do it all?
So far you folks have been awfully helpful (and tolerant) with my questions, and my wife and I are ready to get moving on our project. A new idea cropped up that I’m skeptical of, but would like some other noggins to noodle it over.
We’ve got a 100+ year old church in the midwest (3 hours south of chicago). We’re turning it into a single family residence. It will be two stories with a bedroom/bathroom stack using an as-yet undecided method of heating/cooling. It will be possible to thermally separate the bed/bath area (for the most part) from the sanctuary of the church, which is where we’re having the biggest trouble deciding what to do. This will he an area of 30ftx50ft, with cathedral ceilings 16ft at the roof edges and 31′ at the upper roof peak. It will be our living/dining/kitchen area with a fairly open plan. Right now the sanctuary ceiling is stripped out, exposing the original scissor truss system and plank sheathing. We like the “topless” look so much, we’re wracking our brains about how to keep it like that (open) without owning our own natural gas substation.
We’ve already looked into raising the roof (there’s a thread here on it already) and insulating on the outer side. That’s pretty cost prohibitive, and we’ll still need a heating solution.
If we use forced air of any sort we have to fill the whole volume just to heat the bottom 6-8ft of height, and all that hot air will fly out the uninsulated top without any hesitation.
So I’ll put my head on the chopping block and ask: What if we retro-fitted radiant floor heating, and also added radiant wall panels and didn’t do a thing about the roof?
Assume also we’re would be framing all the walls with 2×4’s and cellulose, leaving the original plaster and lath in place behind it.
Is there any reasonable expectation of keeping things heated this way in a cost effective manner? I’m comparing this to closing off the ceiling again and insulating the attic space along with a forced air system.
That’s it. Be gentle =)
banned from the nail gun
Replies
Radiant will reduce stratification, but an uninsulated ceiling is beyond a horrible idea. It's atrocious, and nothing you do will make it ok except insulating. Radiant will make it simply horrible, instead of incredibly horrible with a FHA system.
Now, you might be able to insulate the cathedral roof in some way, great. But it must, must, must be insulated.
Maybe re-roof with some SIP panels or something?
-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com
Rob;
I wish you wouldn't be so vague... How do you REALLY feel about it? =)I kind of figured that would be the response. Never hurts to ask. We've looked into the SIPS route on the outside. We already have a nice, leak-free roof, and I hate tearing all that off.Let me ask more generally - would radiant be the way to go for this situation, assuming we do proper insulation. Is it the best way to handle large open spaces in colder climates (vs forced air)?------------------------
banned from the nail gun
The higher the ceiling, the better radiant is comparitively to any convective or FHA system. Definitely a good choice there.-------------------------------------
-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com
I can back up what NRTRob said with experience. Our office is in a renovated auto garage. We sublet from the primary leasee; they have the front half, we have the back. Walls are one layer concrete block (no insulation), with steel joists overhead. Bottom of the joists are 13'-6" above the finish floor. Their side has compressed fiber panels sandwiched between the joists . . . our side has nada.When it's really cold outside (20 degrees or less), its 55-60 in here for most of the day. And when it's really hot (90 and above) it's sweltering in here. We were told we have an identical mechanical system as the other side, but in the winter if there's a 40 degree difference between inside and out, our system can't keep up. Their side isn't great, but it's a lot better than our side. Another note: there's a loft on the other side (about 8'-0" above the floor) that we use for storage, and it's a good 10-15 degrees warmer up there in the winter.I like the exposed look too, but I'm glad we don't pay for the utilties here. If you insulate the roof you can take off the shingles and use a product like Celo Vent panels (http://www.dowstyrofoam.com) that have the insulation, air vent and a second nailable deck for shingles all in one panel. It's additional $$$, but your heating bills may make you reconsider.In addition, we have ceiling fans as well, but I doubt their effectiveness. They just seem to blow the air around.
Hi,I would not discourage you from radiant -- I think its a great way to heat, but (at least in my limited experience) the reduction in stratification you get with radiant tends to be exaggerated in the advertising.I have a tall cathederal ceiling living/kitchen area, and measured the stratification:
http://www.builditsolar.com/References/Measurements/strattest.htmThere was only about a 3F difference between the 2ft and 14 ft levels.
I've done this in two houses now with the same result. It does not even seem worthwhile to use the ceiling fan to stir up the air with only a 3F difference.--
Also agree that no ceiling insulation would be a really bad way to go.Gary
Gary, what is the heating method in that room, and what is the load of the space?-------------------------------------
-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com
I need to learn some terms as I get into radiant - stratification sounds to me like layers of differing temperatures. If that's the case, why is one better than the other when you've got the wide-open overhead space with a high ceiling?Also, I believe I've talked the wife into going with Icynene under the old roof sheathing and then proposed cutting and mounting car siding on the inside to cover the foam. This would leave the scissor trusses exposed, and we could stain the car siding to be similar to the old sheathing we liked. Plus the car siding (probably a pine variety) could be cut, stained, and installed by me, rather than having to go with drywall contractors for a "normal" ceiling.*sigh* that's a lot of siding to cut. =)Anyway, The focus would then be on the wals and floor in terms of insulation and radiant systems. There are a number of good sized windows in the sanctuary, and a 3/8" original wood floor we intend to keep. Is radiant up to the task if we supplement with wall mounted panels?How do windows affect the capabilities of a radiant system?Thanks again for everyone's advice.------------------------
banned from the nail gun
Generally radiant is better at reducing stratification of heat because a much smaller portion of its output is from convection (heated air) which is the cause of stratification (hot air rises). This generally means that your peak is not as hot as it would be with a convective (Forced air or baseboard) system. This should result in an increase in efficiency. As gary shows though, each building is apparently different ;)-------------------------------------
-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com
It might behove you to get some HVAC software and run the manual J calculations on all the different options to see what seems to be the most cost effective. Just be sure the software will deal with your existing construction materials and space.BTW, I think ceiling fans may help you the most in the summer. I use our third floor one set on reverse and I open the skylight to exhaust the warm air. It really helps a lot. In your case, you might install a couple of ceiling fans near the very top, if you have some type of opening that you can exhaust hot air through. But you might also be able to install some type of whole house fan, particularly if you are doing roof work.I like the idea of insullating from the underside and covering with siding. Seems very reasonable to me if you really don't want to remove the existing roofing material.Good luck! Your project sounds really interesting.
Thanks Bryan;
So far it's the only compromise my wife has considered "good". We obviously didn't want a completely typical house when we bought a church, but I'm willing to pick my battles more carefully when it comes to certain features - i.e. it will still be a neat interior, whether we have a lower drywall ceiling, or whether we expose the trusses. Yes trusses are nicer (pretty rough and imperfect, but still nice) to look at, but the work to put siding around them at that height will be... lots of fun >=|We'll see if she's right.------------------------
banned from the nail gun
"BTW, I think ceiling fans may help you the most in the summer. I use our third floor one set on reverse and I open the skylight to exhaust the warm air. It really helps a lot."It's probably the skylight that's helping, not the ceiling fan (although it might facilitate the air somewhat). You're creating a stack effect with the open skylight, which is old-fashioned southern air-conditioning. On big southern mansions you often see an ornate 'box' on the roof with slats in it . . . called a belvedere. Does the same thing.
Yeah, I realize the ceiling fan is just an adjunct here, but I've done it both ways (with and without the ceiling fan) and the ceiling fan does make a contribution. Not as much as a true house fan I'm sure, but at least more than the heat put off by the fan motor. But you are correct that most of the benefit is from leaving the skylight open. At least if it doesn't rain.I've seen those boxes with slates, but never knew what they were called.Have you ever been to Monticello? It has a big ring of candles designed to draw the heat up and exhaust it. At least I think it is Monticello, maybe Mt. Vernon.You must have missed our annual community yard sale on Saturday. 3 years in a row it has rained. Forecast all week was for sunshine. We donated or threw out twice as much as we sold.
i just like to use the word 'belvedere' (reminds me of a Bugs Bunny character) ;)
Your community yard sale sounds like it's starting to compete with The Memorial. And it was just like you said, no rain forecast. Rained half of Saturday, then on and off Sunday afternoon. At least it gave me an excuse to watch some soccer on t.v..
Don't know if you're interested but there's a public design session we're hosting Saturday, July 7, to come up with ideas for Main Street between 18th and Berkeley. It's an all-day event, supposed to be a lot of architects and community members to 'design' concepts for renovating buildings, new buildings and public landscaping. Also to develop some kind of farmer's market out there. I think Olde Town East is being invited, but we're still hammering out details. Might be some media attention also. Give you a chance to try out that new drafting table . . . :)
Hi Rob,The house is heated with forced air -- Propane.The cathederal ceiling area is 20 by 39 ft with the ridge running in the 20 ft direction -- peak is 16 ft high.
The east wall has lots of window area.I get a UA loss for this room of:
Ceiling 23
Walls 42
Windows 77 (208 sqft)
Floor 0 (over heated area)
Infil 90 (at 0.5 ACH)
----------
Total 232 BTU/hr-FThe house is in SW Montana (8000 dge-days)-- the furnace runs fairly often on most winter days, so that may tend to keep the air stirred up. I did the same measurements on my last house in Seattle, which had a smaller high ceiling area, and got roughly the same result.
Is this less stratification than you have seen in your experience?Gary
http://www.BuildItSolar.com
Yeah it is. It looks like your FHA is cycling like mad and running near continuously until your deep night time setback?Part of the complication with stratification is that air temp is reduced as heat is lost. For instance, I had to troubleshoot a system around here that wasn't keeping up. Ceiling surface temperature was 50 degrees. That wasn't "super reduced stratification" or "reverse stratification", that was a poorly insulated ceiling sucking heat out of the space like mad. But still, your results are interesting. I suppose if you have a good convective loop that could explain it with a consistently circulating stream. I'd like to see the sensors in the vertical air stream from the registers to the peak to see what the air is really doing as it comes out of the register.. maybe down the other side too.. but that's just curiousity, obviously stratification was not a major problem in your buildings. You did something right I guess!-------------------------------------
-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com
Hi,
"Yeah it is. It looks like your FHA is cycling like mad and running near continuously until your deep night time setback?"Its cycling about every 10 minutes -- I guess I should see if I can adjust the thermostat to increase the on/off temp range a bit?
The part after 11pm is the night setback....
"I suppose if you have a good convective loop that could explain it with a consistently circulating stream. I'd like to see the sensors in the vertical air stream from the registers to the peak to see what the air is really doing as it comes out of the register.. maybe down the other side too."You've got my curiosity up on the flow pattern -- I'll have another go at it next winter. Seems like a little smoke pen or the like would also help to see where the currents are?Gary
You're an experimentalist at heart, aren't you? That would be cool!I'm not sure what regular cycling for a FHA system is. Every ten minutes doesn't sound insane to me as long as it's not running for very short cycles.-------------------------------------
-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com
Would installing insulation on the outside of the roof be a possibility?
Thinking a bit out of the box, you might even be able to buy prefab SIPs and secure them to the existing roof deck.
Did you say topless?