Warmboard with Ductless System?
Rodgo| Posted inMechanicalson
Newbie here, so pardon my ignorance.
我们即将开始德西gning a home in the DFW area (Zone 3).
Home will be a 2-story open concept with about 5,000 to 5,500 SF, properly insulated for the area. Despite the size, plans are to go with about 20 KW of grid-tied Solar Panels with a Powerstation 247 system.
Wife wants “Warmboard” as the heating source for at least some of the areas. I would like to have a VRF Ductless System for cooling and heating. Is there anyway to marry the two so that we stay “married” ?
Wife would like the Warmboard flooring specially on the Family Great Room and Bedrooms/Bathrooms.
Any suggestions would be highly appreciated.
CG
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Is your wife concerned about comfort? If she has previously lived in poorly sealed and insulated homes, I can imagine that being the underlying issue. If you build a "pretty good house" (see this site for details, your new home will be quite comfortable--without the added expense of a second heating system that isn't likely to see much action in your particular climate. (I'm assuming that DFW is Dallas-Ft. Worth.)
With all due respect Steve , comfort does not become of less importance in a well built tight house , neither does it become any easier to achieve . Comfort is not an air temp but instead an experience . There are many proxies to achieve thermal comfort as a standard ( ASHRAE 55) .
Rodgo ,
There are actually ways to achieve what your wife and yourself would both appreciate . They do not necessarily require a separate boiler and an elaborate system design either . Matter of factly it can be achieved with several manufacturers equipment placed outdoors or it can also utilize your water heater (possibly) for space heating . Warmboard is very cost prohibitive but there are other products that do not suffer this .
No doubt many frequenting GBA will tell you exactly what you want to hear but if you're looking for peace with the wife it very well may be worth your time to research and talk to some who have done this successfully .
An inexpensive ductless will certainly keep you cool and warm , your wife may even be tolerant of that but she may always feel slighted . First cost may be much less of an issue than you think , will hear on GBA or have been told .
An electric boiler operated under floor thermostat won't use a lot of power if operated in conjunction with a ductless heat pump that maintains the room temperature. A 73F floor in a 68F room would use quite a bit of power, but a 73F floor in a 73F room uses nearly zero power (only what it takes to overcome room air stratification.) When in doubt, bump up the setpoint on the heat pump, leaving the floor thermostat alone, but at a comfortable temperature.
For a lot of money one could install an air source reversible chiller (eg Chiltrix:http://www.chiltrix.com/) that operates at mini-split type efficiency, but that's a significant up front expense for heating just a few select sections of floor, and the amount of local design expertise and product support is probably pretty small compared to ductless heat pumps.
In order to make rational decisions it's important to have fairly refined and accurate load numbers for the areas intended to be heated at least partially by floors, but also for the ductless system. Since you are at the design phase you have a huge amount of control over the load numbers. Modeling and refining the house using a tool such as BeOpt is highly recommended at this point in the game.
https://beopt.nrel.gov/downloadBEopt2
It's likely that you won't need anywhere near 20kw of PV to go Net Zero Energy, and there are trade-offs to be made, such as higher performance lower-gain windows vs. more PV vs. up-sized heat pump. But in DFW take a look at the "whole-assembly-R" columns for the zone 2 row of Table 2 in this document:
https://buildingscience.com/sites/default/files/migrate/pdf/BA-1005_High%20R-Value_Walls_Case_Study.pdf
Even though Dallas is technically on the warm edge of zone 3, PV efficiency has improved 25% and ductless heat pump efficiency by ~15% since that document was drafted, and the installed cost of PV has dropped by 65-70%, which moves the bars a bit. At roughly that level of performance it should be fairly easy to hit Net Zero Energy with heat pumps with an array that fits comfortably on the roof.
You've gotten good advice from Steve, Rich and Dana already. In particular, Steve is correct that a good envelope leads to excellent comfort, and makes the particulars of heat delivery less important. Rich is correct that comfort depends not just on the air temperature but on other factors. Some of the other factors than decrease comfort are cold drafts and cold surfaces. A pretty good or better house will pretty much eliminate those, and will be quite comfortable. Another factor is everyone's comfort with the decision making process, so it's good that you are taking her input seriously.
他虽然达纳是完全正确的,你可以at a floor to room temperature without a lot of energy cost, if the room is heated by a mini-split. But you also want experience much comfort gain from doing that, compared to just a well-insulated floor. For experience it as a warm floor, you would want to deliver all the heat through the floor. Even then, it won't be very warm if your house in insulated well: if the floor was very warm, the whole house would overheat.
I am a fan of the Chiltrix systems, even though Dana's caution about the challenge of finding local expertise is a real issue. That might be the best option you have to satisfy both residents' wish lists. I also like it because it uses less refrigerant than mini-splits and is less likely to leak the refrigerant and damage the climate. Dana says it's expensive for heating just a few sections of floor, but I'd use it for heating and cooling the whole building, ganging additional units if needed.
The operating cost of an electric boiler to heat a few rooms is a LOT cheaper than alimony! :-)
But as a general rule, it's premature to go too far down the road on the mechanical systems (or the size of the PV array) until you have a much firmer grasp on the loads they have to manage.
Wow. Steve, Richard, Dana and Charlie, Thank you all for such quick responses to my question. I've been lurking for a while and finally decided to ask a question. I appreciate all the responses.
Dana的评论可能不需要20kw of PV, this would be great. The goal is definitely net-zero, but I know this will be difficult as I didn't mention the pool, hot tub, the Tesla, etc... :-(
Should I expect our Architect to help with the load calcs? Or should we go straight to a HVAC consultant? We are still interviewing Architects. This is my first time building a house. So I just need to know the proper questions to ask and who to go to for help.
1) Charlie/Dana, how does the Chiltrix system would integrate with in-floor heating? This is intriguing. If Warmboard is too cost prohibitive, what other products could your recommend?
2) The one aesthetic issue I noticed with Chiltrix just now by glancing at their website (that the wife wont like) is that there is no Cassette in-ceiling option that is flush with the ceiling. The only ceiling option is a mount, where the unit is exposed.
3) I told her I am worried that given our climate in N Texas, the house will get too hot for us to feel the warm floors like the wife wants if the house is well insulated. She liked the idea from a friend's house that has the floor heating (warmboard). This family keeps the floor warm at the same time as they run the Cool Air from their mini split system....I thought they were nuts, but the home did feel super comfortable. Cool air with warm floors.
Thank you again.
Also note that a 73F room (or sealed crawlspace) below your 73F room means that the floor will be at 73F. Without in-floor heating.
A well insulated/moderate climate house with radiant floor is often going to suffer from "when I heat the floor enough to be really nice, the room overheats". But this can be addressed with minimal coverage (eg, a place where you sit, not the whole room).
Let the archtects & engineers (and NOT the HVAC folks) run the load calculations, but also suggest running the BeOpt simulations.
Unless you're driving 1000 miles/week (or in "Ludicrous Mode" most of the time :-) ) the additional amount of PV to run the Tesla is surprisingly small. At typical capacity factors for PV in Texas it's likely to come in at 3-4kw.to drive 15-24,000 miles/year, assuming you can avoid the temptation to embarrass every muscle car you encounter with the superior torque.
Solar-thermal (not PV) pool heaters are more efficient and less costly than PV + electric boiler or PV + heat pump pool heater, but again, until you have a handle on the load there's no way to say how much it's going to take. Clearly an Olympic venue sized pool is going to take a lot more than the average residential pool in Texas. Actively cooling the pool would require a heat pump, but SFAIK most people aren't going there (yet). ECM drive pool pumps can take a large bite out of the operating cost of the pool.
Ducted hydronic air handler coils with ceiling registers is one way to get the co-planar ceiling aesthetic- it can look like any other AC grille. Chiltrix uses First Co. ECM drive hydronic air handlers with their system. (First Co, is headquartered in Dallas, BTW.)
http://www.chiltrix.com/documents/Chiltrix-FirstCo-VMB-Specifications.pdf
Thank you Dana. Are there any other Chiltrix competitors in the US? I see Daikin has a few units, but not for sale in the US.
你把上面我的评论(6.3号),在哪儿e these people were running their warmboards at the same time as their cooling from their Mini Split system?
"This family keeps the floor warm at the same time as they run the Cool Air from their mini split system....I thought they were nuts, but the home did feel super comfortable. Cool air with warm floors."
I think that's completely crazy from an energy perspective, although I do find it plausible that some people were would find it comfortable. If you had to do it, using a water-water heat pump would be a good way to do it--the heat pump would simultaneously deliver chilled water to the fan coils and hot water to the floor. You'd still need an outdoor air to water heat pump to balancing things out most of the time. But the energy consumed by the water-water heat pump would be being used just to indulge this silliness, and would contribute almost nothing to the actual space conditioning.
I think that if you want that effect, a more energy efficient way to get it would be to wear warm pants and take your shirt off.
Ha!!! Good point! As far as other options (more cost efficient) than Warmboard, what else is out there that could be used with a Chiltrix system?
Rodgo ,
Spacepak ( Solstice) and Sunboard . Sunboard , about half the price of Warmboard , shipping will vary but Sunboard is a lighter product per sq ft . Not a structural product though . More tube density , lower water temp requirements . Every job I've done with Sunboard and a separate sub floor assembly has cost less than Warmboard when all was said and done .
The Chilltrix or the Spacepak units will both heat and cool . The Space Pak is a high velocity system however but uses a buffer which allows you to avoid short cycles and shift loads possibly .
Dana stated that you should leave the design to the architect . I disagree . Spend some time finding an integrated design and delivery team and let them tell the architect what the assemblies will look like and perform . Architects are not really best suited for this , structural and mechanical engineers only have jobs because architects don't understand physics . Look up Chris Laumer Giddens , he actually does get it , not sure if he deals with water though .
Dana also mentioned solar thermal for all your other needs mentioned , actually a very good idea , especially for your house and toys .
Jon R , Nonsense but true . Just not too many capable of understanding assemblies and their interaction with the structure they will operate in . We're working on that though .
Your friends house is an interesting thing . I'd bet that the A/C system was poorly designed and does not deal with latent loads well therefore they have to keep the house at 68 . A well designed system should keep you very comfortable at 74-76* . Probably also got sucked into the really high SEER trap , too much air , hardly removes moisture , too many CFM . You know , the typical HVAC guy set up , this is the guy Dana refers to , such a shame . keeping the radiant on to have warmer floors is kinda crazy , how cold would the floor be in an adequately conditioned , 50% RH environment that is 75 * ? Not cold at all . Don't make the mistake your friends did , do it once , do it right and save money and sanity for a lifetime . Be comfortable my friend and remember Integrated Project Design and delivery
Another thing to keep in mind is that in Dallas, assuming a tight, we'll insulated house, the heat will hardly ever be on. As an example, I'm in Maine. The heat was shut off a week ago. The last three days have seen temps ranging from the low 30s to the high 40s, with heavy overcast and no sun at all. Interior temps haven't gone below 70. Two people, a dog, a cat and appliances seem to produce enough heat to obviate the need for running the minisplits.
Our April weather is comparable to Dallas winter weather. Why bother with floor heat when you'll hardly ever get to benefit from it?
"Dana stated that you should leave the design to the architect ."
Not really. What I actually said was:
"Let the archtects & engineers (and NOT the HVAC folks) run the load calculations,..."
The load calculations, not the design.
While some HVAC contractors are competent to calculate the loads, those calculations are unfortunately botched far more often than not by HVAC contractors. When the house design is subject to change it's even more likely to get screwed up. While it can be an iterative process, changes in load as the house design evolves needs to be tracked, and that's more readily done by the house designers. The HVAC folks should be given the load numbers & updates as the design begins to finalize, leave it to designers of the building envelope to come up with the load. Some architects are competent to calculate the loads, others are not. When not, they need to have their engineers run the numbers, and let the HVAC people figure out the options for serving those loads.
There are of course exceptions to the rule- there ARE HVAC people who can do yeoman work on keeping track of the loads of an evolving design, and if you have one of them, please post their contact info!
Guys, again. Thank you for all the responses. Wife is coming along and agreed that radiant floors are not a priority for her. This is good news! Now once we have a preliminary design for load calcs we'll be able to focus on deciding whether to go with a VRF Ductless Heat Pump system or a Chiltrix kind of system.
Rodgo, chiming in late here, but as someone who has recently researched heated floors in a high performing home I feel I should add this. Also should add that much of my critical thinking on the matter was (correctly) initiated by advice given here, and I expanded it on my own. My thoughts are also relative to a climate MUCH colder than Texas, I'm in Ottawa Ontario, where heating requirements are much higher.
The higher performing your building envelope, the less "warm floor" feeling you will have, since less heat output will be required to keep the house at your desired temperature. While I have not finalized our design quite yet, initial calculations indicated if I heated all of the main and second floor of our home, only about 7 BTU/sqft would be required on the coldest nights, down to -30C (-22F) and below on some occasions. This is with ~R45 walls and an R60 ceiling and decent triple pane windows, nothing too crazy.
The other thing to consider with heated floors is, the lower the BTU/sqft requirement the less the higher performing floor options make sense since they cost more. I'm not sure if you ever got a quote for Warmboard or not, or what your budget is, but I was absolutely flabbergasted at how expensive it was. Perhaps someone could justify it with labor savings in a build with a very poor performing building envelope, but considering the cost of the floor that money would be MUCH better spent on considerable upgrades to the efficiency of the rest of the home and HVAC equipment. In my humble opinion, most customers buying these products are those with more money than, well, you know.
I did not get quotes for any of the more affordable options mentioned above once I realized how low the heat requirement of a good envelope would be. At the far end of the spectrum, and just for perspective, the uber-insulated Passivehouses sometimes get by with simple small electric resistance heaters, and even in relatively cold climates.
Anyway, just some perspective from a soon-to-be home builder who did some research into the heated floor thing. I still haven't ruled out heated floors completely, but if I do decide to do them it will be a VERY simple and cost-effective implementation compared to the fancy floor sheathing route. I have no doubt those products perform very well, it's justifying the cost that doesn't add up, for me anyway. As always, YMMV.
Thank you Lance. It looks like we both ended up agreeing to remove the radiant heat from our project. Next step once we are further along will be to decide between an Air-to-air heat pump vs air-to-water one like Chiltrix mentioned above.
RODGO,
I am glad to see your interest in the POWERSTATION 247.
Please contact me directly at[email protected]to discuss the parameters of our system further! We have certified installers in the DFW region who can assist you with the installation process.
Cheers,
Adam Gerber
[email protected]
239-302-9309