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What type of heat would you install a brand new house with the following specs:
2400 sq ft log home with full walkout basement
natural gas
cathedral ceiling and loft for the second floor
9100 ft elevation in Colorado, somewhat (Painfully?) long winters
High efficiency wood burning fireplace in greatroom (i.e. Xtrodinair or similar) (not masonary)
Huge wall of windows facing south. Colorado has INTENSE sun 300 days a year.
Aluminum clad double-pane windows by a good company. Will cover with something like honeycomb blinds to try to keep some heat in at night.
I want radiant heat set at a fairly low temperature then we’ll let the sun warm things up more during the day and the fireplace at night or on cloudy days. Hubby thinks with our sun we are going to FRY during the day and isn’t too keen on the idea that you *have* to light a fire at night to warm the place up. Given all this solar radiation, are we better off with a system where we can easily adjust the temperature? Something like forced air? How responsive is radiant heat to thermostat changes? Our impression is that the response time is very long, like a day. Is that incorrect?
Oh, no air conditioning is required, and there will be porches to help keep sun out during the summer. attached below is a picture of something similar, just without the walkout basement (I hope this works)
So, those of you with experience or just opinions, What would you put in? By the way, hydronic baseboard isn’t too appealing since we’re spending major bucks to have beautiful log walls.
Replies
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The best way to control the sun is through overhangs. Ideally they should be sized to block the summer sun and allow the winter sun.
What's the floor made of? Is it a slab with radiant tube installed? Is it gypcrete? Is it tubing under wood? Each have different warm-up and retention rates. For example, on our 1 1/2" gypcrete floor, I leave the heat off all day and then turn it on at 7. By 10 or 11 the rooms have gone from 66 to 68 or 69 and retain warmth all night. Our slab floor, by contrast, needs at least 8 hours of heating before it gives any back, and then it's good for maybe a day and a half, depending on outside temps. If you pick the floors, I can comment better on how radiant would work.
*My climate is similar to yours, although you get more, higher-angle sun.You are right to be concerned about the solar input with a slow-to-respond heating system.My first floor and loft area are heated off a 4" radiant slab on grade. With two layers of 1/2" ACX covered by 3/4 hardwood flooring. Takes about 12-15 hours to respond to changes. So I deal with summer sun by opening windows (the house is tight enough that I turn the heat off May-Sept). Some day I'll get around to installing a thermostatically controlled ceiling fan to vent the hottest summer air to the attic (and hence out the gable ends).I would recommend radiant in the slab in the basement where I assume you don't have huge glazed area. Since you are already pouring the slab, the distribution of heat in the tubing won't cost much more than duct work would and will result in very even temperatures and warm feet. You MUST have a thermostat with a tight differential (1 degree or less, standard thermostats have 3F differentials). Because the slab is slow to respond you can't have it swinging too far in either direction. A fancier control with an outdoor reset will adjust water temp or duty cycle to compensate for outside temperature. That may be overkill for a basement, but get the 1F diff thermostat for sure. And run extra wires to keep your future options open, especially in a log house! If looking for those smarter controls that can account for solar input and the rate of change in the temp, look for terms like "anticipator circuit", "fuzzy logic", or PID control" for these more sophisticated thermostats ($200-400).If you use radiant upstairs, I would certanly use radiant tubing between the joists rather than gypcrete - cheaper and more responsive. Most people recommend foil-facing foam board under the tubing to direct the heat up to the floor. I agree it should be used, but prefer it for a different reason. Without the insulation, you will also be heating the room below, like those old radiant ceiling systems. That's a bad control scheme to have one system (tubes in the joists) heating two different areas each with their own thermostats.Some spec the aluminium plates. I prefer to run hotter water and save the $$$ and noise. Note that while the source of hot water can be same, you need two different tempering valves because the water to the slab is much cooler (80-95) than water to the joists (120-160). I find my radiant tubing in the joists take about 2 hours to respond.Or go forced air upstairs. If it is a tight house and with the warm basment below, it could be a modest system. Look for smarter controls that can account for solar input and the rate of change in the temp. Terms like "anticipator circuit", "fuzzy logic", or PID control" might be used in these more sophisticated thermostats ($200-300).
*Thanks VERY much for the info. Jim, We were leaning toward the gypcrete for the main floor, and hydronic baseboard for the basement and the loft floors to save some money. Perhaps the stuff under the joists would be better for this application. We will have porches and overhangs to control summer sun, and we can always open a window if its too hot, but its the winter sun when the heat is on that worries me. The sun really is intense during the winter months.David, thank you for all your information. Its super helpful. We'll have to mull all this over and decide. I guess the good news is that we're lucky to have such great sun to heat the house. We just have to figure out how to manage it.
*Paula: Something else to consider are windows tinted to cut the solar input. It's a tough call because on the one hand, the sunlight is free heat and you probably are building where you are because of the views, like us (www.alaska.net/~dthomas/ournewhouse.html)On the other hand, that winter sun can be so intense, you end up hiding in the east rooms at the end of the day (which for us comes about 11:30 pm in the summer). -David
*Paula, I haven't used RFH under a wood floor w/o thermal mass, so I can't comment on efficiency/comfort of that.Gypcrete is expensive, but I like if for our bedrooms because it's fairly quick to heat and it retains the heat just long enough. We don't heat the bedrooms during the day be/c we aren't there. They heat in a few hours in the evening, and hold the heat till morning.I like our slabs in the main living area. Slower to heat, but more consistent. We're there more often, so the consistency is nice. I have not found that a heated slab and the sun combine to make things uncomfortable. If the sun is intense, the room gets hot, regardless of slab heating. The only problem I've seen is the sun heating the room air and turning the floor's thermostat off before the slab is warm. I'm switching to slab-contact thermostats in sunny rooms.I'd guess that tubes below wood floors provide heat faster, but have little retention. I think you also have to run them hotter, because air is a poor conductor. Am I right on this, David? Does that mean the system runs more than with thermal mass options, or is it a wash?The big surprise for me with RFH was how fast the slabs really did heat. Much faster than I thought they would. A pleasant surprise.
*Paula, Don't miss the opportunity to put heat tubes in your concrete floors!!!!! You will regret not doing that later on. BTW, I agree completely with David, he offers some excellent advice as usual.
*A massive (Russian) masonry fireplace with outside fresh air supply.This is Item #1 on my list of features for a new house.(Maybe in my next life....)Cut back on some of the windows and put the money into this monster then build the house around it.
*Jim: Yes, tubing between the joists of a wood floor (no gypcrete) definitely heats faster AND needs a much higher temperature in the tubing. If I'm barefoot, I can notice the difference between bays with tubing in them and ones without through the carpet. (I have one unheated bay on each end because I didn't want to open up another 300' roll or 1/2" PEX). The system does not necessarily run more of the time that a gypcrete system. There's some temp (maybe 90F in the gypcrete and 160F in the joist tubing that drop the same amount (such as 10F) so that they both deliver the same heat (at the same gpm). If they were both operated at 90F, the joist tubing would have to run MANY times (10x? 20x?) longer to deliver the same heat and there may not be that many hours in the day. -David
*Thanks again everyone for your expertise. This is a really great discussion and I hope that others have found it useful too. David, you are so right about the tinting. I mean, of course we want the free heat from the sun, but too much of a good thing is too much! We are thinking that we will probably live in the house for a year and then figure out how much, if any, tinting we may need to have put on. Alan, we have already ruled out a masonry fireplace for the same reason we are concerned about radiant heat: too much sun. My understanding of a masonry fireplace is that you build the fire and then the heat radiates out for 8-12 hours. Once you build the fire, there's no turning back, the heat is there. A truly wonderful thing, really, unless you get the kind of sun we do. Anyway, I had read that masonry fireplaces weren't really recommended for rooms with a lot of southern exposure and sun. And then there is that other annoying factor...the budget. Those things are expensive!!!
*Ah....the budget thang.Which is why I thought the diversion of funds from some (or many) of the South facing windows to the masonry structure would be a fair compromise. I bet they cost a fortune also.With "too much sun", I'm wondering about the immense potential of supplemental DHW heating with (home made) collectors.Not matter what, I envy your situation - too much of a good thing.You are very fortunate to have a dilemma such as yours.Alan
*Alan, are suggesting that I should make *gasp* sacrifices? I think you make some excellent points and yes I am lucky to have such a dilemma. Not only will those windows bring in sun, but they point to a beautiful view. So, I guess you could say, I can't really lose no matter what I do. I'm a lucky person!! Can I ask what may be a stupid question about solar collectors? During the day when the collectors are "collecting" hot water is the exact time I won't need any hot water for heat. Then the sun goes down and I will need hot water. Does the water stay hot? Do you use gas to kick in and help out? Feel free to ignore this question if it is just too basic. -Paula
*I believe the typical approach would be a large tank that is insulated, which is another cost item.....Some get pretty elaborate with material used.There would be additional schemes that ties this tank into the domestic system and also the means to bypass and purge the collectors when necessary (to protect the pipes from freeze/burst) if the collectors are part of the domestic water loop.Then there's the matter of circulation - gravity or circulator assisted....I am not a hands-on expert so I should shut up before I get boinked over the head by a seasoned veteran.Best of luck to your new house,Alan
*Alan, I would hate to see you get "boinked" on my account! So let me just say thanks for the advice, information, and kind wishes. -Paula
*I'll step in here as a "hands-on expert" having installed about 80 solar hot water systems. Alan is right that you need a tank to store the hot water in and that you either need antifreeze in the panels or a system that automatically drainbacks the water before it freezes. For the antifreeze approach, there is also a heat exchanger (either a separate part or built into the storage tank) to transfer the heat to potable water.Controls are either based on the temperature difference between a thermocouple in the roof panel versus one in the storage tank or the circulator pump is driven by a little PV panel mounted alongside the big panels.For most people, the return on investment is not as good as making the house tight and well-insulated or putting the money into a mutual fund. The exception would the Y2K, black helicopter, listen to too much Art Bell types that have to be off the grid for pyscho-social reasons. Then solar can be a component of the heating system or, if you're willing to change your lifestyle to suit your heating system, the only heat source.As long as you are going to burn something to heat your water (natural gas, propane, oil, wood), solar probably doesn't make sense. If you are going to heat water with electricity, than 1) change your mind or 2) consider solar. -David
*Hi, Dave -I think there are handlful off folks who tinker with solar panels as a means to supplement the conventional DHW system.Just a simple setup that send the water through the panel loop when there is sufficient solar gain.Probably more for the fun and satisfaction from seeing something work rather then banking on a dedicated system.I see such systems propped up on roofs (private residences) in the university town we live in.As soon as I become proficient in sweating copper during the plumbing upgrade in the house I would like to experiement with a small setup but make it modular for future expansion. I'm sure there's plenty to be learned but lots of fun at the same time.Thanks for your post.Alan
*I also live in Colorado (at 6700 ft) and have a large southern expanse of windows and radiant floor heat in a thick( 4") concrete slab. I experience very little overheating on sunny days using the following control setup. I have a system that uses continuous circulation with outdoor reset and indoor temperature feedback, employing injection pumping to control the system supply temperature. What this means is, that there is an outside thermistat that controls the temperature of the water circulating continuously through the heating coils. When the air outside gets colder the temperature of the water in the system is increased, and as the temperature outside goes up the system temperature is decreased. Using indoor temperature feadback the system takes into account the indoor air temperature when adjusting the system water temperature. The control that does this is a Tekmar 363. Additionally, when the sun is beating on the slab in out greatroom, the rest of the house gets heated because of the continuously circulating system water - the heat from the greatroom slab is carried to the rest of the rooms in the house, even the cooler north facing rooms. So keep your southern facing windows and use either concrete or gypecrete for you floors for thermal mass - you'll be happy you did. If your looking for a good hydronic heating professional in Colorado, contact Mark Eatherton in Denver. Go to http://www.heatinghelp.com, check the wall forum - you should be able to contact Mark there.
*Alan: I agree that playing with solar can be fun and eductional. And if you are only paying for materials then the payback can be quite good (plus the added benefit of not spending money on other hobbies while you're plumbing).I have always like the elegance of thermosiphon systems. If you can locate the storage tank above the collectors, then all controls and pumps are eliminated. Use antifreeze and all freezing concerns are eliminated. There are hot water tanks with heat exchangers built in. Using one of those lets you do a pretty simple system. And if it could be place in you attic or upstairs, you get the height you need. Maybe you need a new garden shed whose southern side would serve as the collector.The other simple (no pumps or wires) I've seen is quite clever. The panels are on the roof, but function like a coffee percolator. Alcohol boils in small diameter tubing, rising several feet to a collection header and hence creating enough head to drive circulation through the rest of the loop. -David
*Thank you Tom for your response. Its good to know that others in a similar environment have this system and it works. You bring up the point of thermal mass. The logs add a bunch more thermal mass, so maybe they will help regulate temperatures as well. I'm not really sure. The log home companies sure want you to believe they will...but we'll see.
*Hi, David -Thanks for your comments, which is encouraging to someone who wants to tinker with this.Been looking at some 1970s era books that discuss hotwater solar panel construction, and most rooftop gizmos I see around our university town seem to be of similar vintage. Some have plexiglass tops that have become very hazy and the panels may not be used anymore.I am going to start simple and become more elaborate, hopefully at an exponential rate.Take care,Alan
*Alan: Another approach is to buy a commercial panel or two and spend your time and creativity on the rest of the system. The commercial panels acheive a number of things that are hard to create on your own. Low-e tempered glass (sometimes double pane), special high-absorption black coating on the copper risers, sheet copper absorption plates bounded to the risers, rigid foam insulation on the back, all wrapped in anodized aluminium. The ones I was installing 15 years ago could, with no flow, get to 300F in full sun. And there are better glass types available now. -David
*I just can't help butting in here and reinforcing something that David said. Getting domestic hot water, or heating from solar hot water systems is a fine hobby. It is nice to play with if that is your bag. But as something that the average homeowner can install and live with like normal systems; forget it.Since the house is already built options are limited. One that has not been mentioned but that I've seen used effectively is sheers over the windows. It is amazing how much energy is reflected by them without interfering with the view. Sheers can be put on rods so they can be opened and closed at will. They are cheap, can be color coordinated with the interior decor and are not permanent so can be changed easily.
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What type of heat would you install a brand new house with the following specs:
2400 sq ft log home with full walkout basement
natural gas
cathedral ceiling and loft for the second floor
9100 ft elevation in Colorado, somewhat (Painfully?) long winters
High efficiency wood burning fireplace in greatroom (i.e. Xtrodinair or similar) (not masonary)
Huge wall of windows facing south. Colorado has INTENSE sun 300 days a year.
Aluminum clad double-pane windows by a good company. Will cover with something like honeycomb blinds to try to keep some heat in at night.
I want radiant heat set at a fairly low temperature then we'll let the sun warm things up more during the day and the fireplace at night or on cloudy days. Hubby thinks with our sun we are going to FRY during the day and isn't too keen on the idea that you *have* to light a fire at night to warm the place up. Given all this solar radiation, are we better off with a system where we can easily adjust the temperature? Something like forced air? How responsive is radiant heat to thermostat changes? Our impression is that the response time is very long, like a day. Is that incorrect?
Oh, no air conditioning is required, and there will be porches to help keep sun out during the summer. attached below is a picture of something similar, just without the walkout basement (I hope this works)
So, those of you with experience or just opinions, What would you put in? By the way, hydronic baseboard isn't too appealing since we're spending major bucks to have beautiful log walls.