View Single Post
Old 02-02-21, 04:16 AM   #26
randen
Uber EcoRenovator
 
Join Date: Apr 2011
Location: Strathroy Ontario Canada
Posts: 657
Thanks: 9
Thanked 191 Times in 129 Posts
Default Heating a slab for solar space heating

The utilization of solar heated hot water for heating a concrete slab for space heating is Nirvana!! On all accounts its a home run for: saving money, complexity, and comfort.

Here in Canada our winter weather is a little harsh. But I have once described the comfort like this. "On a cold windy morning standing infront of a window with a coffee in hand watching the wind swirl the snow around with my sock feet on a porcelain HEATED floor is the most comfortable feeling know to man!!!"

I have 220 sqft of flat plate solar collector on a south facing wall. with a full day of sunshine from 10:00am til 4:00pm will warm the concrete slab to 28 Deg. C which will store enough heat for 24 hrs. and hopefully the next day more sun!!

Complexity well start with planning!! The concrete slab has to be well insulated a minimum of 4" HD foam insulation under. the slab an 2" around the edge to mitigate any heat losses
Tubing in the floor. There are a few manufactures of this product designed for this application Wirsbo comes to mind. They have a complete system of manifolds valves etc. This tubing is tied to the weld mesh thats in the concrete at a foot apart. There is a lot of information now on lengths required in the loops.
DO NOT over control these loops!! IT is NOT necessary to sense and control the temperature of the zones!!! The liquid heating of the slab is very uniform and thats what you want. KEEP IT SIMPLE!!! Choose a central location in the house and place a thermistor (install a little well for the Thermistor it maybe necessary to replace) in the concrete between the loops to control the slabs temperature/Circ. pump.

DO NOT consider storage tanks, buffer tanks, mass storage (tank with boulders) Phase change materials ETC.! I know I probably made some enemies there. But hear me out: You cannot store enough water and keep it insulated and manage the pumping, heat transfer and the cost for all this is overwhelming. KEEP IT SIMPLE.!!

THE CONCRETE SLAB IS YOUR HEAT STORAGE.

We have experienced power outage (no power for circ. pumps) in a winter storm. The concrete floor maintained enough heat during that event for THREE DAYS.


To heat the floor with solar make a DEDICATED hot water loop in the floor. Hot Water/Glycol (propylene Glycol for freeze protection) Employing a small circulation pump, small expansion tank and Mixing valve on its own manifold. Having a dedicated solar heating loop raises the efficiency doing away with heat exchangers ETC.

KEEP in mind your goal of heating with the sun cost nothing going forward.!! Depending on the amount of sun in the winter SOLAR has provided HALF our homes heat!!

Install a second loop offset the tubes in the concrete in the middle of the dedicated solar loop. You will also need a manifold and small circ. pump and expansion tank. This will be your supplemental heat if you don't receive any sun.!! Your heat source here is your choice Propane boiler Demand heater Wood boiler or the King.... HEAT PUMP

Dedicated loops just saved you costs in both efficiencies and extra costs related to heat exchangers and valving. Plastic tubing is cheap by comparison.

Space heating is the largest energy cost for the home. Solar hot water heating is direct and no energy conversions like using Solar PV. and inverters ETC.

It works, we've being living with solar space heating since 2008 saving energy saving money and very comfortable

Randen
randen is offline   Reply With Quote
The Following 2 Users Say Thank You to randen For This Useful Post:
jeff5may (02-02-21), skyking (12-22-21)