evacuated solar tubes + GE geospring hybrid water heater for radiant floor heat?

[SKY888]

Hello,

I'm from RI, and I have been using my GE geospring water heater since last December 2012.

Even with the coldest day up here in the Northeast, the GE geospring water heater runs 100% "heat pump" mode down my unfinished/unconditioned basement. The coldest the basement got was around 44 degrees, but the hybrid heater still able to manage to squeeze out every beat of heat from the air.

I chose it over evacuated solar tubes because National Grid Power reimbursed Rhode Islanders $1000....which is what I paid for the unit itself. So basically it's free.


so here's my question, I would like to add radiant floor heat on my 1000 square foot (first floor). Placing those PEX tubing in between the joist.
I am not planning to heat up my 2000 square foot colonial with radiant floor heating......since I already have central forced air (propane). But it would be nice to have warm floor during winter since I'll have a toddler roaming around the first floor soon (she's only 4 months now)......plus I'm hoping that radiant floor heating will save me a bit from heating bills.

I know that the GE geospring water heater will not be able to give enough juice to run the radiant floor heating.

That's why I was thinking of getting evacuated solar tubes so it can run the radiant floor heating.

Either I integrate it with my current GE geospring hybrid water heat and get a heat exchanger so I can seperate the DWH and the radaint floor heat. Or completely seperate the two systems. To just run the evacuated solar tubes directly with the radiant floor heat?

The reason why I want to integrate the evacuated solar tubes with my GE geospring hybrid water heater so I can fully utilize these tubes all year.......and not just during winter to heat my radiant floor heat. And if I integrate them, those evacuated solar tubes will definitely help my hybrid heater during winter.

so my questions are:
1.) should I integrate them or not? if yes, why? if no, why?
2.) how many evacuated tubes should I get in order to get enough BTUs to run a 1000 square foot floor with PEX radiant tubes?
3.) Are evacuated tubes be more economical/practical/ideal for my plan? or you guys just recommend another source of heat source?
4.) I thought about just buying a regular electric water heater, and use it as a heat source for that 1000 square foot radiant floor system. Its the cheapest heat source but I'm just scared of the electric bill. I know other people have done it, and they said it "warms" the floor a bit, but dont expect to heat the living area.
5.) any other thoughts?
6.) will flat plates be more economical and ideal?

thanks for the help!

[LucMan]

Simple answer to all your questions: Solar thermal of any type, evac. tube or flat plate is a poor choice in the Northeast for space heating. Not enough sun hrs. to be effective during the cold months.

If you want to use electric to fuel your radiant flooring a Daikin Altherma heat pump is the only way to go at this time, but be prepared for a high initial installation cost.

[russ]

I have radiant floor heating and it is comfy for the toes but would I ever do it again? No!

Expensive to install and operate.

The Daikin Altherma is 1st class but I would use standard split inverters - unless the weather in your area is too cold for heat pumps.

[SKY888]

Simple answer to all your questions: Solar thermal of any type, evac. tube or flat plate is a poor choice in the Northeast for space heating. Not enough sun hrs. to be effective during the cold months.

If you want to use electric to fuel your radiant flooring a Daikin Altherma heat pump is the only way to go at this time, but be prepared for a high initial installation cost.

thank you for the response.


As much as possible, I would like to be economical if I'll install radiant floor heating. My bro-in-law from out of state will charge me $3000 for installation of pex tubing/manifold/pumps (including parts). I think that price is very cheap especially for 1000 sq foot space.

I just need a heat source to run the radiant floor system. If the cost of the unit and install price will be too expensive.....I guess, I'll just scratch the plan off

Daikin Altherma heat pump is awesome, but the upfront cost will be brutal to my wallet

[SKY888]

I have radiant floor heating and it is comfy for the toes but would I ever do it again? No!

Expensive to install and operate.

thanks for your honest opinion!

whats your heat source?

and what energy you use? oil/nat gas/electric/propane?

[russ]

ASHP - air source heat pump - air to water

[SKY888]

even with ASHP, your radiant floor is still expensive to run, huh?

how big is the space and do you mind sharing how much it cost during the winter season?


thanks

[russ]

even with ASHP, your radiant floor is still expensive to run, huh?

how big is the space and do you mind sharing how much it cost during the winter season?


thanks

In floor radiant you don't turn on and off - once it goes on in the fall it stays on. You can't make rapid adjustments in temp with in floor - up or down.

How big is of no consequence as we only heat part of the 6,000 ft2 area though 3 floor have infloor radiant and four have fan coils.

The fan coils are of far more use than the in floor radiant.

Cost - relates to nothing as we keep most of the house quite cool.

[SKY888]

yes, I think putting infloor heat on set-backs is not ideal. You just need to leave it on the whole time and keep it stable.


During winter we just keep our central force air temp at 64 degrees, and turn on an additional infrared space heater when we are at the living room, or at master bedroom. This combo is the most economical for us.
Wood floor at the living room and ceramic tiles in the kitchen are freezing tho...lol.

If I remove the infrared space heaters.....and just bring up the temp of central forced air to 68-70, the propane bill just skyrockets big time.

That's why I was thinking of a ways to heat the first floor and make it comfy, without a huge installation cost and operational cost.

[russ]

For in floor radiant you really need the thermal mass to go along with it. My floors are concrete and fine for that purpose.

[inetdog]

I have radiant floor heating and it is comfy for the toes but would I ever do it again? No!

California home builder of the 1950's, Eichler, went for in-floor radiant for his open-style single story homes. It was very very comfy, and avoided the need for fans, ductwork or registers. It gave you reasonable comfort during a California winter, even with mostly glass single-pane walls in the main rooms.
But it would not be economical with today's energy costs, and the copper coils in concrete started to leak like sieves after a few years. There are better materials to use these days but the fundamental economic problem remains.

[LucMan]

The cost to heat a home is dependent on the local climate, the size of the home and the insulation value to keep the BTU's that you pump into the home from escaping outside. Additional insulation should always be your first choice as you only pay for it once, whereas the fuel bill keeps coming as long as you live in the home.
Radiant floor heating is an excellent choice if in concrete because the the floor is the your radiator. Wood floors not so much, insufficient thermal mass. In recent years I have been using old school wall hung steel radiators (Buderus) with great success. They have excellent thermal mass, respond well to outdoor reset water temps, and are less expensive to install than the radiant floor tubing and yet offer the occupants equal comfort. Take a look at them before you go with radiant floor heating, just size them according to the projected water temperatures that you will be using. Lower water temps will of course require a larger radiator.

[SKY888]

thanks for the honest input guys.

I really appreciate it.

Our electric company (national grid) actually pays about 70% for insulation upgrades/air leak fixes.

I'll be paying about $700 for this company to add 7" cellulose insulation and use of spray foam to all the crevices/holes/etc that can be found for air leaks......in my 1000 sq foot attic. I think, I'll have around a total of r-50 after adding the 7" cellulose insulation on top of my current fiberglass insulation on my attic.

hopefully this will help alot for next winter.


And since most of you guys are swaying me not to go with radiant heat on my wood flooring due to the install/operating expense, I guess I'll just scratch that off for the mean time.

thanks.

[inetdog]

And since most of you guys are swaying me not to go with radiant heat on my wood flooring due to the install/operating expense, I guess I'll just scratch that off for the mean time.
thanks.

With a wood floor rather than a concrete floor, the thermal mass is a lot lower and you can get a relatively quicker response. But the wood is not as good a thermal conductor, so you may end up heating the space under the floor as much as you heat the floor. You would definitely have to insulate well under the heating elements on the bottom of the floor unless it is a basement or lower floor that you also want to heat anyway.

[Naptown]

California home builder of the 1950's, Eichler, went for in-floor radiant for his open-style single story homes. It was very very comfy, and avoided the need for fans, ductwork or registers. It gave you reasonable comfort during a California winter, even with mostly glass single-pane walls in the main rooms.
But it would not be economical with today's energy costs, and the copper coils in concrete started to leak like sieves after a few years. There are better materials to use these days but the fundamental economic problem remains.

So did Aurther Levitt and sons in the 40's and 50's
Same deal with copper and leaks in the floor.