I'm about to pull all my hair out!

So I just purchased a half-built home that is about 2700sqft. The first level is slab on grade with a concrete radiant floor (1800sqft), being driven by an Hydro Shark II Electric Modulating boiler (14kw). This is the only heating in the home, besides a wood burning fireplace. The house has all ICF foundation on the 1st level. I will be putting R-45 spray foam in the ceiling (on the metal roof) and then R-30 in the 2nd level wall cavities. The home was designed to be Passive Solar, but there are some huge tree's directly south to where the windows are, so I'm not sure how much heat gain I'll get via the windows.

I was wondering if someone could help me to figure out if this is a good system to have? what should I put upstairs, which is basically 900 sq ft and anything else I might need? With the system as it stands, how expensive is it going to be to heat the place, if everything is electric? vs a propane system? There is no natural gas, so it's either electric or propane.

My frustrations come in when I've had an Energy Star for Homes expert come in, as well as a Radiant Floor / HVAC specialist and they both told me it will cost 3-4 times as much to heat the home with this system. They gave me a HERS index of 117 (incomplete data because I don't have the window specs) with current system and told me if I do a High-Effeciency boiler, my index would be around 70 (I'm trying to get some rebates). I then got a quote from the HVAC guy to do a HE boiler system, w/ indirect water tank, baseboards upstairs for $20k with another $5k for an ERV system.

Also, there is no domestic hot water in the house at all yet as well, so that has to be addressed. The house uses well water.

Does anyone have any thoughts? I'm pulling my hair out figuring out what I should do? Then there also is the option of going Geothermal as well? I'd like to use what I have, but if it's not going to be Energy Efficient it might not be something I want to do, or regret later? I called the company that supports the Hydro Shark II system and he said I should run it for a few months to see what the costs are, then decide whether or not to go with a boiler system. But with that said, it would cost more to install that type of boiler system when the house is complete as opposed to with open walls.

I'm spinning my head here, and appreciate any help anyone can give me.

The home is in Charlton, MA and hasn't been finished yet, follow the link below to see some images:
http://www.flickr.com/photos/reeboo...153381257/

Thanks,
Ryan

heating with electricity in MA is nuts, I believe. UNLESS, you have almost no heat load. which may be true in a high mass home with great passive solar. If those trees are deciduous they may not be a big problem for your wintertime solar gain.

Sounds like you want to see how much the passive solar 'works' if you can. that's a big X factor. the propane would undoubtedly be cheaper to run, but without knowing the passive solar contribution it's quite a moving target to guess what your operating costs will be.

I would attempt to match the rest of your system's water temp with emitters upstairs. read that as "not baseboard". maybe a radiant ceiling, if they are flat and not drywalled yet. that's pretty cheap and fairly low temp. but that's a guess. without a load calc for the upper areas it's hard to say what is good and what isn't up there.

I'd hold off on the boiler replacement. someone needs to figure out that 2nd floor question though.

Thanks for the quick response. It's tough because I'm sure they designed the system appropriately and it like why would they spend all this money on a concrete radiant floor with Electric boiler if they didn't think it was going to work? In the original plans it called for an additional boiler with baseboard heating upstairs. I was thinking about keeping it all electric, using small wall mounted space heaters or something. I was also looking at a 5kw Solar PV system but am wondering spending 30k on that will just help reduce the cost of the electric heating, if the case it doesn't seem worth it... Also was looking at Solar Hot Water as well. There are so many options its tough to decide.

I think regardless tho I have to do the ERV system correct? In order to get fresh air in/stale air out of the home since it will be so tightly sealed?

you absolutely need a fresh air system. I would use an ERV myself, there are cheaper options but not really better options. it's best if you use an ECM motor unit for very low power usage. venmar has an HRV (EKO) that fits the bill, there is the UltimateAir Recoupaerator... I think lifebreath offers some ECM options as well.

if you can't wait on the 2nd floor I don't know that I'd recommend electric resistance emitters, since you already have a hydronic source I'd lean more towards the radiant ceiling or panel radiators for low-cost, low-temp hydronic alternatives.

PV to supplement heating again only works if your heat load is very low. Otherwise it's "farting in the breeze" as the wise ones say. Solar thermal is great for DHW. for heating, same as PV... only good if your heat load is low or panel array is very large.

lots to think about!

ERV is a must, ok. Is this something that a DIY'er can install or does it need to be put in by an HVAC pro? thanks for the info on this.

Would I be able to do panel radiators off the current system that is installed? Basically add the panel radiators to the system for the radiant floor?

The Solar PV was gonna be 5kw. I wish the Solar Thermal could integrate into the Hydro Shark system somehow to help?

ERV installation is not rocket science but it does take some design and figuring to get the ducts right.

panel radiators can work off of your current system but they would need to be sized for very low temp water.

5kw is nice but it's not enough to heat with for most people. solar thermal can integrate with hydronic heating. but typically unless your array is huge you suck up all the BTUs showering without much left over for heating in the winter.

again though in your case it's very hard to say what is needed with the big X factor of the passive solar. Your heating system may be true "backup" or it may be primary heat with passive solar supplement... one would like to think whoever designed it knew what they were doing, though. maybe if you could get a passive solar consultant in there...

Thanks for all your help. I'm going to put up a post in another thread to see if anyone knows of any Passive Solar Consultants in New England, MA area.

If the design day heat load of the house is anything like 14kw, a heat pump solution might be cost-effective. (Maybe even something like the Daikin air source hydronic system at Rob's office.) Even at MA electric rates, the operating cost of ground source heat pumps is less than natural gas, and the Daikin system would have an operating cost less than half that of an electric boiler, maybe close to 1/3 the cost in Charleton MA, and you'd still be "all electric", if that buys you a favorable rate. (I assume you're in the National Grid service area?) But heat pump solutions are many x the up front cost of an electric boiler- enough that it might make sense to heat it with the boiler for a season to test the affordabilty.

Running an electric boiler with PV is ridiculousy inefficient. Commercial silicon PV runs ~15% efficiency at the panel, plus inverter losses, etc. Solar thermal flat-panels at radiant-slab temps will buy you ~50% efficiency on average- you get more than 3x the heat per square foot of panel out of the deal, and more than 4x the heat per $ invested in hardware. But if the building is designed for high passive gain, you'll need significant storage capacity to make any active-solar worthwhile, since when you have the most active-solar to collect, you also have the biggest passive boost.

This screams for a real heat-loss analysis before moving forward. Hopefully your passive solar consultant will be able to estimate better what you really need.

not just heat loss: heat loss doesn't model passive solar gain. that's why I made the recommendation. a pure heat loss would call a passive solar window wall a huge heat sink.. which it is, but only if it's dark or cloudy.

not helpful for yearly energy analysis, which calls that window wall a heat source, not a heat loss.

Posted By NRT.Rob on 20 Apr 2010 04:10 PM
not just heat loss: heat loss doesn't model passive solar gain. that's why I made the recommendation. a pure heat loss would call a passive solar window wall a huge heat sink.. which it is, but only if it's dark or cloudy.

not helpful for yearly energy analysis, which calls that window wall a heat source, not a heat loss.

You're absolutely right!  In my mind I was thinking "gain/loss" but somehow the "enter" pinky is quicker than the brain today!  (What, just TODAY?    )

The heat loss numbers would only tell how big to make the backup system.

The Daikin air source system looks like an option. I'd love to keep it all electric if I could but I guess it depends on the initial system cost. The quote I got from a highly reputable HVAC person is $20k for an HE boiler, Indirect Water Tank, with hydronic baseboard upstairs. I don't really want to spend that amount of cash at this point.

But I just got off the phone with someone from ZeroEnergy Homes out of Boston, MA. He claims that if the house was designed properly, the things that installing an HRV system would allow me to heat the upstairs by bringing the warm air into the upper level, then just using some electric baseboards as 'backup' which I might have to turn on a bit in the winter time. And then leave the current Electric boiler setup and just test it out for a season or 2.

So I know I need the HRV or ERV system ($4-5k)

I had a thought, let me know what you guys think? What about if I swapped out the Electric Tankless Boiler for just a Propane Tankless? Like a Rheem unit? $700-$1000 for that, get a propane tank installed, etc. Just purchasing a unit to run the radiant floor. Then doing a Solar Thermal System for my whole house hot water needs? Would that make sense and be energy efficient as well as keep the cost down? I got a quote for the Solar Thermal last month, 3 panel system with Rheem 120 gallon tank w/ Electric Backup for $9500, after tax rebates will will be about $5500. It seems like couple with the HRV system I could do all that installed for about $12-13k after rebates as opposed to $25k HE boiler system.

Hmm...

do not replace the electric tankless until you know you have to. if the solar gain is good, any replacement would be a waste of money.

Ok,
My only concern is I'd like to get Energy Star for Homes Certified, and with that Electric Tankless I fail. My HERS index would go from 117 to a 70 just by replacing that boiler. Adding Solar Thermal would make it go down even more.

I see.
with a single slab zone, the tankless idea is ok. I'm not sure if you go to HERS 70 by using a water heater instead of a high efficiency boiler for heating though, do you?

That's what they told me. It might to be 100% accurate but she said if I swap out that Electric Tankless for a HE Propane/Gas boiler it would go down into the low 70's

I mean, that might be true if you use a HE propane/gas boiler. but an on demand tankless is not a HE propane/gas boiler; it's a water heater. I'm not sure it will help your HERS rating. but I'm not sure how HERS is calculated either... just be aware you are talking about two different types of heat sources that are not interchangable.

Ok thanks, that makes sense.

HE water heater with plate heat exchanger and hydronic panels. Condensing gas appliance for space and domestic hot water. Perhaps a certified designer could help?

Solar thermal will heat about half your DHW (most of that in the summer months).