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the_glassman
Registered Users
Posts:8
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| 05/31/2008 11:17 PM |
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| From the onset of designing my SIP home I've had my heart set on hydronic radiant floor heating in the slab in the basement and through the joist on the main floor. I originally intended to go with a DX Geo-exchange unit to supply BTU's required for my setup, but soon found out that it doesn't make sense in several key areas:
Lack of local installers and knowledge
Price
Space requirements for the loops and and the unit itself
Still requiring a secondary source for DHW needs
Did I mention price? ;)
I recall a thread on this forum that highlighted the fact Geo is a rather lavish setup for a well sorted SIP or ICF house.
I'm already investing the money into having R40 walls, R60 attic space, Thermotech windows, etc... However this has still left me without a viable heat source for my floors.
Due to the volatile prices of LPG and the other nasty stuff associated with it, I've also ruled it out as well. So no mod/cons for me.
My first thought was a whole house tankless. While they are praised for having no standby losses, they require a lot of electric and appear to have efficiency advantage when it comes to radiant heating applications.
I've looked into solar, but don't think I'll have the additional funds to allocate at this time for the extra upfront cost.
Which brings me to a recent discovery while surfing the net tonight.
http://www.airgenerate.com/
An air based heat pump for DHW. It connects to any standard tank heater and claims to be the most efficient way of heating water. It's also more affordable than a lot of the other options I've looked into.
What I'd like to do is get one of the larger (50+ gallons) super efficient (EF .95) and insulated electric tanks and add this to it. Also since I'm getting a well insulated water heater (storage tank) I could incorporate some solar elements down the road and already have a suitable storage tank and backup for many rainy and cloudy days we have in Upstate New York
Am I nuts or could this possibly work and maybe be even some what efficient and cost effective? |
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engineer
Registered Users
Posts:315
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| 06/09/2008 9:17 PM |
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There are (very few) heat pump water heaters out there - They are marketed for both increased efficiency (COP of 2.0 or better) as well as for providing 'free' cooling and dehumidification for basements, garages, crawl spaces, etc.
What you will run hard up against is that in Upstate NY you have a relatively high heat load and such cold days that an air source heat pump will work very poorly, if at all, during the coldest days. They've gotten better, to be sure, but I doubt any would perform satisfactorily without substantial resistive backup during mid-winter |
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Without data, you only have an opinion. |
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dmaceld
Registered Users
Posts:469
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| 06/11/2008 12:34 AM |
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My thoughts. Take a look at the Daikin heat pump system for house heating/cooling. It will kick out heat down to 10F outdoor temp before it switches to auxiliary heat.
There are alternative units to the AirTap, but not many.
The AirTap DHW heater looks very interesting, and the price is not unreasonable. I'm considering getting one. I would put it in my garage (I'm building the house now) which is ICF and well insulated. The garage will have it's own heat/cool unit connected to the Daikin outdoor unit. That way, during the winter, I'll be putting heat into the garage from outdoors with an efficient system, the Daikin, and then transfer that heat into the hot water tank with a second efficient system, the AirTap. During the summer I'll have cooling in the garage from the AirTap which will reduce the cooling load on the Daikin.
I probably would install it in a separate water heater and use it for preheating the DHW, which would be connected in series with another electric water heater to raise the water temp to 140F +.
So, if you have an efficient heating system in your house and/or garage and install the AirTap to get it's heat from there, it may just work out for you.
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Building house - what a way to spend retirement! |
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giantsridge
Registered Users
Posts:2
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| 06/22/2008 10:47 AM |
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"During the summer I'll have cooling in the garage from the AirTap which will reduce the cooling load on the Daikin."
I'm confused- how will you get summer cooling from the Airtap at a time when your garage heating system is not calling for heat? It wouldn't be operating in the summer, would it?
Secondly, why the recommendation to use the Airtap as a water preheater? Is this because you need 140F + degree water for your particular hydronic system?
I've been looking at the Airtap system as well, but don't see it as a cold-climate solution (I'm in Minnesota). However, I do see a benefit for DHW heating in the summer months when the exhaust air can be utilized for cooling. I was going to install it on an electric water heater and just use the airtap during the summer months... |
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ian_upton
Registered Users
Posts:10
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| 06/23/2008 8:28 PM |
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Glassman,
What type of SIPs are you planning on using and what thickness?
How does one get R60 in a roof. I thought a 12 EPS sip had an R value of about 45.
Ian. |
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BadgerBoilerMN
Registered Users
Posts:70
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| 07/01/2008 2:12 PM |
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ModCon with indirect. It is sealed combustion so you won't blow up! If that is your concern. Domestic hot water is the kicker and nothing more hot water for less money than a ModCon. The typical "tankless" is 82% effiicient (note the stainless steel flue) and standby losses are usually less than 5%. If it doesn't condense, it ain't much.
A ModCon is also the perfect match for radiant floor heating.
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MA
www.badgerboilerservice.com |
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dmaceld
Registered Users
Posts:469
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| 07/04/2008 12:00 AM |
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Posted By giantsridge on 06/22/2008 10:47 AM
"During the summer I'll have cooling in the garage from the AirTap which will reduce the cooling load on the Daikin."
I'm confused- how will you get summer cooling from the Airtap at a time when your garage heating system is not calling for heat? It wouldn't be operating in the summer, would it?
Secondly, why the recommendation to use the Airtap as a water preheater? Is this because you need 140F + degree water for your particular hydronic system?
I've been looking at the Airtap system as well, but don't see it as a cold-climate solution (I'm in Minnesota). However, I do see a benefit for DHW heating in the summer months when the exhaust air can be utilized for cooling. I was going to install it on an electric water heater and just use the airtap during the summer months...
During the summer both the Daikin and AirTap will be removing heat from the garage air. The Daikin will dump it outdoors and the AirTap into the DHW tank.
The reason for using the AirTap as a preheater (note this is for DHW only, not space heating) is to make sure the AirTap does most of the heavy lifting in heating cold water for DHW use. The second heater, in series, will bring the water up to 140F for dish washing, etc. Even though many are recommending DHW be set only to 120 or 130F it is generally accepted that 140F is the minimum for sanitary dish washing. And, I like to have my water hot! Also, the AirTap by itself won't meet the plumbing code requirement for First Hour Recovery for new residential construction.
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Building house - what a way to spend retirement! |
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the_glassman
Registered Users
Posts:8
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| 07/04/2008 9:53 AM |
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Posted By ian_upton on 06/23/2008 8:28 PM
Glassman,
[quote]What type of SIPs are you planning on using and what thickness?
How does one get R60 in a roof. I thought a 12 EPS sip had an R value of about 45.
Ian.[/quote]
I'm using R-Control panels. However I'm not using them for the roof. (I know, I know) Instead I have raised heel (energy) trusses.
I plan a very thick layer of closed cell spray in foam for the attic.
I did it this way for a couple of reasons. First, the home was built by my wife and I with very little help or equipment. Getting the panels on the roof between the two of us would have been impossible. Secondly, because I'm still not 100% sold on closed attic. Especially here in the north east of the country. Also there is less conditioned space with this approach. |
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the_glassman
Registered Users
Posts:8
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jbishopcomm
Registered Users
Posts:3
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| 08/11/2008 10:57 PM |
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The Air Generate product only produces 7,000 btus. No matter how many storage tanks you try to use, 7,000 btus is still 7,000 btus. So this is ruled-out.
As for solar, while I'm a huge fan, it's just not cost-effective to rely on it for year-round space-heating. When you need the btus most, the sun panels just don't produce -- and there's not enough storage in the world to cover what you need. To be practical, think of solar for your domestic water-heating only.
Here's something else to chew on....
Coming as early as this winter, Hallowell International will be launching their "Cube" air-to-water heat pump for cold climates. It looks promising. It will probably run down to about 0 degrees F, so you'll want some sort of back-up. No worries. Keep in mind that despite how cold it gets here (I'm in the Albany area), the majority of our heating-hours are at temperatures ABOVE +30 degrees F. So, for the relatively few hours you're below zero, it won't kill you to use oil or propane as a back-up. If you're going with a hydronic system, consider using a propane-fired Combi-Cor water heater (a standard water heater with a built-in heat-exchanger for space-heating). It's a simple and relatively cheap (cheaper than a separate, direct-vent boiler, anyway).
As for the Hallowell Cube, although no pricing has been released, I would expect to pay somewhere in the $15K neighborhood to have it installed. While it seems pricy, it's far cheaper than the $40k-$60k price tag of geothermal -- with similar results.
Or, if you want something bullet-proof, green, and high-performance, you could always consider a Viessmann wall-hung condensing boiler. Yes, they cost alot -- but you get alot.
Hope this helps.
JB-(www.enhancedliving.net) |
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