Unconventional Heating Idea

Rogue

Hi Everyone,

I'm looking for some thoughts on a crazy idea I had. Feel free to poke holes but please don't be rude (it's just an idea).

I recently bought a home with radiant heat and a boiler (old large hulking radiators in most rooms). The boiler is old and on its last leg.. This house has had three additions put on in the 80's.. two of which were utterly miscalculated for the heating need (these additions also have smaller baseboard heat exchangers hooked up to the same system which might be part of the issue.) Long story short, I want to 'upgrade' and add in floor radiant heat to the house instead.

Now for the fun part... we also have an indoor pool that is attached to the house.. do you see where I'm going?

What I'm wondering is... is it possible to hook up my radiant heat system to this gigantic water tank I call a pool? My only concern at this point are the chemicals.. currently we use Chlorine which degrades PEX from what I understand. I know they make UV systems for pools..

Anyway, I'm thinking of putting a few solar collectors on the roof along with my traditional pool heater. If the temp of the pool is at 86*F and constantly cycling through the house.. do you think that would work? I hate the idea of running a pool heater And a boiler (my gas bill is feeling it as well). I'm thinking the pool filter/heater/pump would stay its own system but then adding a feed and return line to/from the pool and a pump/manifold within the house to cycle the pool water at the correct PSI.


It's weird and crazy and probably unheard of.. but I like it - what are your thoughts?

Jamie Hall

It is neither weird nor crazy. It is unconventional. Nothing wrong with that.

First off, I presume you mean to get rid of the radiators? Some folks like them. Your idea is incompatible with radiators -- they require higher temperatures. And further, I presume that you are in fact able to add radiant heat to the floors? Either through the ceilings beneath or tearing up the floors, because you will need full access to get useful radiant heat.

If those two questions are "yes", then the first thing you need to do -- the very very first -- is to run a heat loss calculation for the structure for each room individually. This will tell you whether you can meet that heat loss with radiant floors.

I would not use the pool water for either the solar collectors or the radiant floors. The chemicals in pool water will happily destroy both -- and if you were to put corrosion protection in the radiant system, you'd not want that in the pool. What I would do is size heat exchangers using the pool water on one side and, for one, the radiant system on the other and, for the other, the solar collector system on the other. This will give you flexibility on chemicals and perhaps just as important on pressure -- particularly if you go to a drainback solar system.

It will take a competent and open minded engineer to work this all out for you. They are out there, but they are a bit thin on the ground.

On the plus side, you may be able, even in a rather northern climate (for example, northern New England), to use solar heat entirely, since you have a very large storage. That will depend on the type and efficiency of the roof collectors.

Ironman

The only way to prove if such an idea is feasible is to have real numbers to crunch: how many gallons is the pool? what's the actual heat loss of the house at design temperature? how much heat contribution can realistically be expected from the solar panels? can a radiant floor supply enough btus to heat the house at design temp?, etc., etc., etc.

You wouldn't wanna connect directly to pool water; a heat exchanger with ancillary components would be required.

But all that adding in the pool is doing is providing a large buffer tank. If the heat loss from the pool is greater than what the solar can provide (which it probably is), then you've accomplished nothing.

A large solar array, on average, provides about 30% to space heating and 70% to domestic heating. Those are very generalized numbers, but adding a large buffer (like your pool) is not gonna change the amount of heat provided. It only gives you the capability of storing more heat. Since solar panels only provide their output about 1/3rd of the day, I don't see where all that storage would benefit.

HVACNUT

On a side note, is there humidity control in the pool room?

Rogue

I hope I formatted these quotes correctly, thanks for all the help!

Jamie Hall said:

It is neither weird nor crazy. It is unconventional. Nothing wrong with that.

Thank you! I was gearing up to be torn to shreds

Jamie Hall said:

First off, I presume you mean to get rid of the radiators? Some folks like them. Your idea is incompatible with radiators -- they require higher temperatures. And further, I presume that you are in fact able to add radiant heat to the floors? Either through the ceilings beneath or tearing up the floors, because you will need full access to get useful radiant heat.

Yeah, I'll be removing all the radiators and installing in floor radiant. The basement gives access to the first floor, I hate the 'popcorn' ceiling in the lower level so we'll knock that out to heat the upstairs (already started). One of the additions is grossly under heated and does not have access underneath so I'm thinking of tearing up the floor and putting down pex/thinset/tile.

Jamie Hall said:

If those two questions are "yes", then the first thing you need to do -- the very very first -- is to run a heat loss calculation for the structure for each room individually. This will tell you whether you can meet that heat loss with radiant floors.

If it's one thing I've learned from reading all these forums, it's to do the heat loss calculation and to do it right

Jamie Hall said:

I would not use the pool water for either the solar collectors or the radiant floors. The chemicals in pool water will happily destroy both -- and if you were to put corrosion protection in the radiant system, you'd not want that in the pool. What I would do is size heat exchangers using the pool water on one side and, for one, the radiant system on the other and, for the other, the solar collector system on the other. This will give you flexibility on chemicals and perhaps just as important on pressure -- particularly if you go to a drainback solar system.

Very good points, thank you. I was reading about putting an exchanger in the pool system and lost sight of that for some reason. It all sounded very economical and made for the 'situation.' Thanks for pointing me back in the right direction!

Gordy

I'm looking at it this way.

What temp will the pool tried to be maintained at?

85 degrees is pretty warm for swimming if even feasible with a solar array in winter.

85 degree pool water won't do much for radiant in the dead of winter unless the loads are very low. You will lose some through the HX .

However shoulder season heating would be an avenue where it might shine. You are still getting a fair amount of sun in the fall, and coming into spring. Loads are low during these times.

It's not a bad idea to try and do something with all that mass, but I just think it would be more dollars to set up than what it will return in useful energy for heating the home. If you like to play though it's not an off the wall idea.

Edit: I should add will the pool be heated because it will be used a lot for swimming, or will it be heated for mostly trying to heat the house. Big difference in how you pursue this.

Zman

I love the concept. I too see swimming pools as giant batteries for heat storage.
I would spend some time calculating a few things before I got too excited:
Heat loss of the building
Supply water temp required to heat the building on design day, and the average day as well.
Heat loss of the pool water to the ground.
Evaporative heat loss of pool.
Available roof space and average wintertime panel Btu output.

Rogue

Ironman said:

The only way to prove if such an idea is feasible is to have real numbers to crunch: how many gallons is the pool? what's the actual heat loss of the house at design temperature? how much heat contribution can realistically be expected from the solar panels? can a radiant floor supply enough btus to heat the house at design temp?, etc., etc., etc.

Pool is 25k gallons - I'm going to start looking into the heat loss.. I'm also not sure about insulation in this old house..something else I'm investigating (I hear insulating older homes typically creates mold issues) But you're absolutely correct - a lot more homework to do. I'm glad you guys are here to bounce things off of though.. makes chasing pipe dreams less likely

Ironman said:

You wouldn't wanna connect directly to pool water; a heat exchanger with ancillary components would be required.

But all that adding in the pool is doing is providing a large buffer tank. If the heat loss from the pool is greater than what the solar can provide (which it probably is), then you've accomplished nothing.

A large solar array, on average, provides about 30% to space heating and 70% to domestic heating. Those are very generalized numbers, but adding a large buffer (like your pool) is not gonna change the amount of heat provided. It only gives you the capability of storing more heat. Since solar panels only provide their output about 1/3rd of the day, I don't see where all that storage would benefit.

My thought here was that the loss would be more easily 'made up' when there is such a large buffer. What I'm looking at is using the solar as a primary means of heating and a pool heater to tip the scales/make up the remainder (instead of having the heater short cycling 24/7)

HVACNUT said:

On a side note, is there humidity control in the pool room?

There are two exhaust fans that currently do a decent job - this question leads into my next thought I'm doing a little digging before I say anything

Gordy said:

What temp will the pool tried to be maintained at?

85 degrees is pretty warm for swimming if even feasible with a solar array in winter.

85 degree pool water won't do much for radiant in the dead of winter unless the loads are very low. You will lose some through the HX .

However shoulder season heating would be an avenue where it might shine. You are still getting a fair amount of sun in the fall, and coming into spring. Loads are low during these times.

It's not a bad idea to try and do something with all that mass, but I just think it would be more dollars to set up than what it will return in useful energy for heating the home. If you like to play though it's not an off the wall idea.

Edit: I should add will the pool be heated because it will be used a lot for swimming, or will it be heated for mostly trying to heat the house. Big difference in how you pursue this.

We typically keep the pool around 78*F. I'm going to look at the heat loss calculator more seriously very soon. I thought typical temps were around the mid/upper 90's for input temps for in floor radiant? I suppose that is a decent difference.. My next thoughts are revolving around a heat pump incorporation