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no heat upstairs in new construction--a bad idea?
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sas778
New Member
Posts:6
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| 17 Mar 2010 09:53 PM |
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We are building a new house and do not want to oversize the heating system. Traditional builders think that our plan is crazy. Does anybody have any insight into whether this will actually work? Here are the details of the construction. It is a 2-story house, 1000 SF per floor, on a basement. The insulation is R38 in the roof, and R25 in the walls. There is a passive solar design on both floors, with insulated shades for the windows (R7) and we are located in VA.
We want to put radiant hot water heat in the downstairs only and no heat in the upstairs. The upstairs is bedrooms and we like it colder in the bedrooms anyway. The manual J calculations say that we need 25,400 btu for both floors. We can get 26,000 btu out of the heat in the downstairs.
The contractors are telling us to put heat in the upstairs just in case we need it, but we'd rather save the $5k and not pay money for something we don't need.
Is this a really bad idea?
Thanks in advance for any advice! |
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Alton
Advanced Member
Posts:754
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| 17 Mar 2010 10:12 PM |
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Will you need air conditioning upstairs? If so and you use central air with ductwork, a future homeowner could still add central heat without too much trouble. Otherwise, I would really be concerned about resale. |
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Alton C. Keown
Residential Designer and Construction Technology Consultant
Auburn, Alabama
E-mail: alton at auburn dot edu |
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sas778
New Member
Posts:6
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| 17 Mar 2010 10:19 PM |
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Thanks for the response!
We're not putting AC anywhere in the house. With good insulation, passive solar design (with overhangs to keep the sun out completely in the summer), insulated window coverings, high ceilings (9-foot), and being far away from any urban heat islands, we think we'll be fine without AC. Other people in the area don't have AC and are comfortable during the summer. If we decide we really need AC, we'll put in a ductless AC system down the road. |
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jonr
Advanced Member
Posts:911
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| 17 Mar 2010 11:43 PM |
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At least put the pipes in for upstairs heating.
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AirSepTech
New Member
Posts:3
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| 18 Mar 2010 04:04 AM |
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It will work but it will be cold upstairs. The bathrooms are the real problems---like 55f@5am. What is not stacked directly above the 2 lower floors will be colder yet. My MB is above unheated garage, gets down to 40f with the door closed and no heat---none.
Details: 980sf basement, no insulation--none. 900sf 1st floor, 1000+ 2nd, 2x6R19 walls, laidup 9/12 hip roof black comp shingles R30. Great solar exposure, low-e argon glass, lots of it.
I built the entire house myself. ManJ/pros calced well over 30k or 50k, I don't remember---I thought THEY were crazy. I put in a lpg DV stove, 30k btu, have never really been cold except the baths and MB. At 65-68 in the greatroom, its 60-65 in the baths/MB. It was the only heat source.
LPG went to $3.10 in Dec. I went total electric. Tried portable H/Pumps at $400x2, and 4 $22 oil filled heaters from Walmart. It is funny, the oil filled won. It is currently 30f on the porch and 65f at the kitchen table, 63f upstairs. Good solar day at 57f. Been like this 3 days.
I had 11 kwh 7am-7pm, 23kwh 7pm-7am. That is my TOTAL energy use, heat,DHW,lights. Last month 836kwh@ $.085.
I have months of tracking, I average 5-7k btu/hr. The highest is 10.5k btu/hr.
I am 20 miles from Elko, Nevada. 6000ft., 7000+ HDD, always 5-10 days @ -20f many more @ 0f.
This house is not finished, drywall is in, 50% taped. Doors and cabinets, no other finish carpentry. Room for quite a bit of improvement. It has become a contest for me.
My other home in Boise is new, 1800sf, no basement, vaulted open plan. Looks great. NG/Electric ALWAYS $150-175/mo, drafty, kids play with the thermostat, feels just as cold or worse. I have lived mostly with forced air heat and hate it. When you get away from it you won't like it ever again.
My plan is to go with the 'new' super efficiant mini-split/inverters as primary, 18-24kbtu max---I think, still debating. The LPG stove will be back up. I really wanted to go with radiant floors, I paid cash as i went, couldn't afford it when I started.
I was also afraid of leaving the house with no heat for extended periods.
If you plan on selling easily, you will need a "real" heat source, for most buyers it is FAU. People are sheep, and only want
to follow the crowd.
I believe your plan will work. You will want heat in the baths, maybe space heat in the beds, electric blankets/down comforters do wonders.
My plan works for me. Low energy use, low bills, low cost. But not for sheep.
Good Luck!!
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dpilati
New Member
Posts:10
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| 18 Mar 2010 07:06 AM |
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Well - it wouldn't pass inspection in NC. Maybe you don't have to worry about such things. $5k sounds like a lot for bargain basement heat for 1000 sq feet. Here we can get heat and a/c for 2000 sq feet for $6500 on new construction but each situation is different and sometimes being smaller doesn't save much money. I have never lived in VA but I've lived above and below. And I would want a/c on new construction anywhere on the east coast. Now maybe you are in the mountains?
I personally would want a heat pump to hit the bathrooms....
We sleep upstairs and put straight heat pump upstairs with dual fuel down stairs. We are less insulated than you and a bit warmer also. We didn't run the heat upstairs this cold winter until we had a baby. Oops - baby doesn't like to sleep at 60 degrees like we do. People are not necessarily sheep but babies are......So for resale, you absolutely should have heat upstairs. Guests don't necessarily like it either - the inlaws sleep at 68.
Passive solar is great but it won't heat your bathroom at 7 am - only active solar can do that or really amazing masonry which is unlikely in a bathroom.
VA is a pretty big state with some significant climate changes in the mountains - you might want to be more specific. Really the best way of addressing these things is with zip code or do the HDD/CDD thing.
Does your wall/ceiling insulation ratio make sense? Maybe your design limits your attic to 38? Around here you would be at code in the attic and just about double code in the wall.
On Forced air: There are so many bad systems out there. It doesn't make forced air inherently bad its just that most of us have lived with bad forced air systems. In a situation where you want a/c, it really is the most economical and least wasteful of resources. I would still do radiant if money were of no concern but you don't see it often in mixed climates for a reason.
Last - What about if you did radiant in the bathrooms . But I'd probably say radiant the guest room too. |
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sas778
New Member
Posts:6
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| 18 Mar 2010 08:05 AM |
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Thank you AirSepTech! That was really helpful to hear about your experience. I agree with you--I despise forced air heat. It is so uncomfortable and inefficient. I feel warmer with radiant heat set at 70F than with forced air set at 75F. All parts of the upstairs are directly above the downstairs. We're thinking of putting an electric in-wall heater in each of the two upstairs bathrooms in case we need them.
Our zip code is 20180 |
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Matt G
New Member
Posts:43
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| 18 Mar 2010 08:20 AM |
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As the previous poster I too live in NC but lived in VA for ~40 years previous. Here mechanical codes require that systems be installed to keep all conditioned areas stay within 4 degrees of each other. As 1/1/10 a new mechanical code came into effect that requires the heating/cooling to be controlled separately on each floor of a multi story house. I have no idea what codes are presently in effect in VA but I know VA building codes are very similar to NC which is separate from mechanical codes. My point being that you have to find out if code would even allow what you are proposing. You could possibly get a pass on traditional means with a very detailed detailed design showing that your alternate means would produce the same result as the code requirement, and here anyway it would have to be stamped by PE.
Secondly, having lived in VA for all that time I'm pretty familiar with the state. To me VA is about the epitome of a mixed heating/cooling climate. Most areas get some snow and also a few 100 degree days. The tidewater has much less snow but far more need for AC. West of I-81 has very few 100 degree days but significantly more snow and just that much more need for heat. There is no place in VA where you could go without AC - or at least not for me as it would result in divorce. 
Re the heat, I guess it depends on how well the passive solar aspect is designed, but I'm very skeptical. That could maybe work, and maybe even well if the house was designed from the ground up by a mechanical PE swho is a solar design expert. A design like that might cost $5k. Does that number sound familiar? And then you still wouldn't have the duct work in place for the AC. Again, the divorce factor.
Mark me down as a contractor who thinks it is a really bad idea. |
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sas778
New Member
Posts:6
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| 18 Mar 2010 08:42 AM |
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Thanks for the opinions!
hmmm...about the AC....I should mention that we are having a very good whole house fan. I grew up not far from where we are living, without AC, and we were perfectly comfortable. We'll add a ductless AC system later if necessary, but I really don't expect to need it.
I am concerned about code. The HVAC person who did the manual J's and the quote for me says that he can have it pass code, no problem. But I'm worried that he doesn't really know what he's talking about and that I will have problems with the county if I don't put the heat in upstairs. Some people at the county have said that it is fine, and other people have said that it is not ok. |
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glenfotre
New Member
Posts:61
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| 18 Mar 2010 10:25 AM |
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Posted By sas778 on 18 Mar 2010 08:05 AM
Thank you AirSepTech! That was really helpful to hear about your experience. I agree with you--I despise forced air heat. It is so uncomfortable and inefficient. I feel warmer with radiant heat set at 70F than with forced air set at 75F. All parts of the upstairs are directly above the downstairs. We're thinking of putting an electric in-wall heater in each of the two upstairs bathrooms in case we need them.
Our zip code is 20180 I'll be the first to admit that I have never, to my knowledge, experienced radiant heat other than direcly from the sun. A serious question that I have regarding radiant heat is "How do you filter all of the dust, pollen, etc. out of the air if it is not circulating through the HVAC system equiped with a filter?" It seems that it would just lie there until 'Mrs. Clean' (I'm married to her) wipes it up. Any thoughts on this??  |
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Dana1
Veteran Member
Posts:1438
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| 18 Mar 2010 11:38 AM |
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Posted By glenfotre on 18 Mar 2010 10:25 AM
Posted By sas778 on 18 Mar 2010 08:05 AM
Thank you AirSepTech! That was really helpful to hear about your experience. I agree with you--I despise forced air heat. It is so uncomfortable and inefficient. I feel warmer with radiant heat set at 70F than with forced air set at 75F. All parts of the upstairs are directly above the downstairs. We're thinking of putting an electric in-wall heater in each of the two upstairs bathrooms in case we need them.
Our zip code is 20180
I'll be the first to admit that I have never, to my knowledge, experienced radiant heat other than direcly from the sun. A serious question that I have regarding radiant heat is "How do you filter all of the dust, pollen, etc. out of the air if it is not circulating through the HVAC system equiped with a filter?" It seems that it would just lie there until 'Mrs. Clean' (I'm married to her) wipes it up. Any thoughts on this??
Without the induced infiltration & drafts of a forced-air heating system there is simply less pollen in the house, and it's not the dust isn't being stirred up by the air currents. Your question belies a common mis-conception about hydronic/steam/radiant heat held by those who have only lived with air-delivered heating systems. Hot air systems spread mold & pollen, and MUST be filtered to achieve good indoor air quality. Water and steam delivered heat just leaves dust mold sports & pollen bits where they lie, to be vacuumed up when you clean. In very tight houses with controlled humidity the only pollen dust & mold that get in are human transported. In less tight houses with hot air heat, the necessary pressure differences required for moving the volumes move some un-filtered outdoor air in through any infiltration path that exists. (10-15% of the air flow volume is pretty typical- which is another reason why in not super-tight houses hydronic systems of equivalent AFUE typically use ~10-15% less fuel that their hot-air cousins when properly sized.) In super-tight houses active ventilation is necessary, in which case a filtered heat-recovery ventilation system is preferred. As for the no-heat upstairs concept, hydronic baseboard is cheap, and in a house with design-day temps above 0F and R26 walls with decent windows, it's dead easy to put in enough baseboard to meet manual-J at radiant-floor type temps, simplifying the heating system design, and should be WELL under $5KUSD to plumb in. Since the whole house heat loss is calculated to be only 50-60KBTU/hr anyway, that's already calling for the smallest size modulating-condensing boilers available anyway- you won't be able to go smaller if you wanted to. Whatever it's peak BTU rating is, look closely at the minimum modulation level to achieve best efficiency. Some 80K units have 5/1 turn-down ratios, with minimum modulation a bit lower than some 50K units. Also, if you heat your hot water with a low-mass boiler like a mod-con using an indirect-fired tank, it'll be as-efficient as a tankless on-demand heater at less than half the installed price. It's more expensive than a standalone tank but has 3-4x the lifespan, and improves the AFUE of the heating system by reducing standby losses due to a higher average duty-cycle. |
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jerkylips
Basic Member
Posts:246
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| 18 Mar 2010 11:47 AM |
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Posted By glenfotre on 18 Mar 2010 10:25 AM
Posted By sas778 on 18 Mar 2010 08:05 AM
Thank you AirSepTech! That was really helpful to hear about your experience. I agree with you--I despise forced air heat. It is so uncomfortable and inefficient. I feel warmer with radiant heat set at 70F than with forced air set at 75F. All parts of the upstairs are directly above the downstairs. We're thinking of putting an electric in-wall heater in each of the two upstairs bathrooms in case we need them.
Our zip code is 20180
I'll be the first to admit that I have never, to my knowledge, experienced radiant heat other than direcly from the sun. A serious question that I have regarding radiant heat is "How do you filter all of the dust, pollen, etc. out of the air if it is not circulating through the HVAC system equiped with a filter?" It seems that it would just lie there until 'Mrs. Clean' (I'm married to her) wipes it up. Any thoughts on this?? radiant heat was on our radar early in the process, but I had the same question you do. The builder told me that with radiant, you still need ductwork & stuff for the central air, so it basically comes down to essentially installing 2 systems - a forced air system and radiant system. That drove the costs higher than we were willing to accept. That said, having the ducts & blowers allows you to get some air movement. Last fall we sold our house & temporarily moved into an apartment that has baseboard heat. One of the "advantages" I've heard about radiant heat is that your house isn't nearly as dusty because you don't have a forced air system circulating all of the dust. I can tell you that with our baseboard heat & no blower, we have plenty of dust. We also have pretty stale, stagnant air. All winter long, I've been opening the patio door to get fresh air into the apartment. Not a big deal when we're not paying for heat, but I wouldn't want to do it if I was paying for it. Long story short, if money was no object I would definitely put radiant heat into my house because it IS more comfortable, but I would only do it if I had some sort of system to circulate air as well. Now that I'm thinking about it, I wonder if radiant heat and an HRV/ERV would be sufficient? |
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glenfotre
New Member
Posts:61
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| 18 Mar 2010 01:32 PM |
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"
"In very tight houses with controlled humidity the only pollen dust & mold that get in are human transported."
OK, so we have a 'very tight house' - how do we control the humidity (I'm in AZ with a humidifier) with no ducting or air movement? Do you plug the humidifier into the ERV? |
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Dana1
Veteran Member
Posts:1438
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| 18 Mar 2010 01:53 PM |
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Posted By jerkylips on 18 Mar 2010 11:47 AM
Posted By glenfotre on 18 Mar 2010 10:25 AM
Posted By sas778 on 18 Mar 2010 08:05 AM
Thank you AirSepTech! That was really helpful to hear about your experience. I agree with you--I despise forced air heat. It is so uncomfortable and inefficient. I feel warmer with radiant heat set at 70F than with forced air set at 75F. All parts of the upstairs are directly above the downstairs. We're thinking of putting an electric in-wall heater in each of the two upstairs bathrooms in case we need them.
Our zip code is 20180
I'll be the first to admit that I have never, to my knowledge, experienced radiant heat other than direcly from the sun. A serious question that I have regarding radiant heat is "How do you filter all of the dust, pollen, etc. out of the air if it is not circulating through the HVAC system equiped with a filter?" It seems that it would just lie there until 'Mrs. Clean' (I'm married to her) wipes it up. Any thoughts on this??
radiant heat was on our radar early in the process, but I had the same question you do. The builder told me that with radiant, you still need ductwork & stuff for the central air, so it basically comes down to essentially installing 2 systems - a forced air system and radiant system. That drove the costs higher than we were willing to accept. That said, having the ducts & blowers allows you to get some air movement.
Last fall we sold our house & temporarily moved into an apartment that has baseboard heat. One of the "advantages" I've heard about radiant heat is that your house isn't nearly as dusty because you don't have a forced air system circulating all of the dust. I can tell you that with our baseboard heat & no blower, we have plenty of dust. We also have pretty stale, stagnant air. All winter long, I've been opening the patio door to get fresh air into the apartment. Not a big deal when we're not paying for heat, but I wouldn't want to do it if I was paying for it.
Long story short, if money was no object I would definitely put radiant heat into my house because it IS more comfortable, but I would only do it if I had some sort of system to circulate air as well. Now that I'm thinking about it, I wonder if radiant heat and an HRV/ERV would be sufficient?
Experience would say "depends". You'd have to model the house well enough to determine just how much solar gain you'd get, and get a handle on both latent & sensible loads to see if nighttime ventilation schemes and a tight house could dump enough heat in your location without incurring a high latent load. High R-values, low solar gain, and nighttime dew points of 55F or less are key to making it work. Outdoor dew points higher than 60F will raise the RH inside to mold-inducing levels on surfaces 70F or lower, but at 55F dewpoints the RH @ 70F is ~60%, the high end for human comfort, but not a mold hazard. If daytime dew points are typically higher than 60F, an ERV is preferable to an HRV, but some mechanical dehumidification may still be necessary. If anybody in the home has dust mite allergies the interior RH needs to be 50% or less, which means nighttime ventilation can only be used if the outdoor dew point is ~50F or less. In my case the sensible loads are relatively low, but the latent loads substantial- dehumidification of ventilation air is a must most of the summer, and periods of peak sensible load correlate highly with increased latent load. A 1/4-1/2 ton window AC unit is sufficient to handle the sensible loads 95% of the time, but the dehumidifier runs a significant duty cycle even when there's no or very low sensible load. (The oversized central AC in my place sees maybe 10hours/year of on-time.) As I've tighened up the place the dehumidifier's duty cycle has decreased. Not knowing the particulars of construction & systems design of your rented space with the baseboard heat I'm not sure what to say, other than that your experience is at odds with the "typical". Have you monitored the relative humidity in that place? Dust has many sources, but using the heating system as the primary vaccum cleaner isn't an ideal solution. There's plenty of dust in my place too, but if we take shoes off at the front door and don't leave windows & doors open it's noticably less. |
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jonr
Advanced Member
Posts:911
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| 18 Mar 2010 02:50 PM |
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> In less tight houses with hot air heat, the necessary pressure differences required for moving the volumes move some un-filtered outdoor air in through any infiltration path that exists.
This effect is pretty much eliminated with balanced fully ducted returns and keeping all ducts away from exterior walls and unconditioned space. Even so, I prefer the quiet of non-air systems.
Circulation of AC, humidity control, radon and ventilation air are legitimate concerns if you try to eliminate ducts.
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jerkylips
Basic Member
Posts:246
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| 18 Mar 2010 04:13 PM |
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Posted By Dana1 on 18 Mar 2010 01:53 PM
Not knowing the particulars of construction & systems design of your rented space with the baseboard heat I'm not sure what to say, other than that your experience is at odds with the "typical". Have you monitored the relative humidity in that place? Dust has many sources, but using the heating system as the primary vaccum cleaner isn't an ideal solution. There's plenty of dust in my place too, but if we take shoes off at the front door and don't leave windows & doors open it's noticably less.
well, it's an apartment with carpet that has seen God knows what. In our house, we had hardwood & tile for the most part. I'm sure that's part of it. So I agree, it's maybe not a completely fair comparison, but it's what I've noticed over the winter. The biggest thing, more than the dust, is just the sense of stale air. If I cook a meal for dinner, I can still smell it in the air the following day...stuff like that. I've been in homes that had radiant heat & I love the warm floors. I think that you need to spend more time than I have to really be able to appreciate it, but I'm sure it's as good as advertised - I just wouldn't do it without some sort of ventilation system.. |
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Dana1
Veteran Member
Posts:1438
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| 18 Mar 2010 04:23 PM |
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Posted By jonr on 18 Mar 2010 02:50 PM
> In less tight houses with hot air heat, the necessary pressure differences required for moving the volumes move some un-filtered outdoor air in through any infiltration path that exists.
This effect is pretty much eliminated with balanced fully ducted returns and keeping all ducts away from exterior walls and unconditioned space. Even so, I prefer the quiet of non-air systems.
Circulation of AC, humidity control, radon and ventilation air are legitimate concerns if you try to eliminate ducts.
With a Manual-D duct design, mastic sealed duct seams & joints, and a return & supply for EVERY room (or large jump ducts/grilles between rooms) the induced infiltration can be reduced to mid single-digit fractions of the total air flow in reasonably tight houses. In VERY tight houses with continuously variable ECM drive air handlers it's probably even lower. Surveys of existing houses in CA built prior to the CA Title 24 2005 standard had typical leakage well into double-digit percentage territory, which is why under Title 24 new construction ducts must be built to Manual-D, and duct leakage tested & rectified as-need to bring it under the defined standard (I can't remember what the particulars of the standard are off the top of my head- I'd have to look it up. You could too.) Very few homes outside of CA are built anywhere near as stringently- the vast majority of existing ducted heating systems in the US would fail both the duct design & leakage test standards miserably. Ventilation air, radon & humidity issues are legitimate concerns in tight house with OR without ducts. Counting on the incidental induced leakage for ventilation air from the heating/AC system is a lousy way to control any of it, and in the low-load conditions of the shoulder seasons the duty cycle of the heating/AC system is a small fraction of what it is during peak load days/weeks/months. Of course the tighter your house is, the less ventilation you get from sloppy ducts/wind/stack-effect, and the more important room-by-room ventilation systems become. I'm not sure how you get circulation of AC without ducts, but in a tight house the interior humidity in all rooms that aren't themselves moisture sources pretty much tracks the average humidity inside the pressure envelope, and simple dehumidification need not be ducted as long as there is at least some amount of air communication between rooms/floors. To cool my antique home with a single window AC unit it's installed in the hottest upper floor room with the door to that room left open. Convection between the cooled room and the first floor keeps the temps reasonably close (not perfectly, of course), and the humidity levels stay more tightly coupled than the temps. The N side room upstairs stays cool enough as long as the door stays open, and the house remains comfortable even when it isn't keeping up with the sensible load, since the high duty-cycle of the unit has significant impact on the latent load as well. (A 45%RH 80F room is as comfortable as a 60% RH 76F room. But every situation is different- there are very few universally perfect solutions that will work in every house. |
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Yggdrasill
New Member
Posts:3
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| 11 Apr 2010 03:36 PM |
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I live in Seattle and we're looking at doing something similar. Of course, our climate is different and we have a basement. It sounds like you are grappling with the issues we are of how to minimize the size of a heating system. HVAC companies are not the place to look for advice on this because: a) the bigger the system, the more money they make; and, b) the last thing they want is a customer calling them in the dead of winter to complain that the heating is on full blast but they're still cold.
While the design is not yet finalized, our approach has been to size the system to meet most needs, and not peak loads. We're actually trying to go with no heating on either floor, except for electric radiant floor panels in the bathrooms. Initially we were going to put in radiant heat downstairs and nothing upstairs (except in the bathrooms), but our calcs came back showing that approach as generating too much heat. We will have a portion of the basement heated with radiant, however.
To go with no heating system upstairs, you must have a very well insulated and tightly sealed envelope. A tight envelope in turn requires mechanical ventilation to exchange stale air with fresh, and that system must absolutely have a highly efficient ERV or you'll be losing heat like crazy.
The builder you talked to is wrong. The ventilation system for an ERV is NOT the same as that for a forced air system. Forced air ducts are larger, moving a greater volume of air at a greater speed. A ventilation system with an ERV, such as is found in passive house systems, is typically 4" ducting. It moves less air at a slower speed.
We're looking at distributing heat from appliances, body heat, solar gain, etc. though the ventilation ducting. For peak loads, when the temperature is really low, we're going to install fan coils in the ducts so they can deliver warm air as necessary. We may plumb radiant to spots on the main floor in case we need to install a radiator or two.
I looked at ground loop heat pumps, but they are pretty large and costly. The system I really want is something like what they use in Europe and Japan, a combination air source heat pump water heater and ERV. The heat pump uses the exhaust air from ducts for it's stuff before it goes to the ERV. I don't think anything like that is available in the U.S., yet, but Daiken has introduced an air source heat pump water heater. This would be for domestic hot water and radiant in the basement. It's pricey, though. However, I can always put in a $300 electric hot water tank and wait until HPWH prices come down, if I can't afford it now.
My advice is that, if you have to have a heating system, go with radiant if you can afford it. Either way, plan on installing a mechanical ventilation system with ERV. Your house should be so well insulated and air tight as to require such ventilation. Depending on your climate, overheating may become a greater issue. Here in the northwest we don't typically have cooling loads, and only the most poorly designed buildings require A/C. Opening the windows in summer will suffice, but our summers are dry. Our old house was poorly insulated but had a basement, and the
mainfloor never in 15 years became uncomfortably warm during the
summer. If you need A/C, a ground source heat pump is a great option in that it does both heating and cooling.
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Rosalinda
New Member
Posts:42
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| 12 Apr 2010 09:38 PM |
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SAS778 - I am trying to do the same thing you are but in a colder climate- zone 5B NY. I installed the radiant tubing in my ground level frost protected shallow foundation slab, which we poured on Friday. I also insulated R30 around the top edge of the slab perimeter, and R10 (well R9 effective) down to 4 feet, hoping the thermal mass in the slab and the ground under it, will heat up to a stable temperature. I will add some thermal mass to the second floor (which is the main living area) using water tubes, but am hoping to do completely without additional heat on that level, than that of solar gain. I am allowing for adding zones upstairs if needed, but since it is just running PEX to either a radiator or some other kind of low temp radiant heater, I don't think it will be too complicated to add at some future date. NY code requires you demonstrate you can keep the house at 68 degrees F when it is 1 degree outside, at a point 3 feet above the floor and 2 feet from exterior walls in all habitable rooms. The use of one or more portable space heaters shall not be used to achieve compliance. Since I am looking to get my CO by June, this will have to be demonstrated via Manual J vs installed system capabilities. At least they don't force you to have X number of radiators etc per room, just that you can show that whatever heating system you have can produce enough BTUs to meet Manual J.
Now all I have to do is figure out Manual J, and decide HOW I am going to heat the water in the radiant floor.
-Rosalinda |
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toddm
Basic Member
Posts:287
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| 17 Apr 2010 02:30 PM |
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I am hoping that an HRV is sufficient to balance heat between my ground floor with many windows and lots of thermal mass and an upstairs without much of either. The HRV you want for this job is a "fifth port" design, which can alternate between recirculation and exchange. My Greentek moves 220 cfm, operated by humistat or timer. I am mounting it in a vertical chase so the fifth port wouldn't need any extra ducting. In the summer, I'll use it to move air around a heat pump water heater, also mounted in this chase.
All of this operates by windage (me guessing at the right interval and fan setting.) But in a passive solar house, a swing of five degrees either way is reason to cheer. |
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