hello, new to the forum, question about passive solar hot water heat..

[Amosunknown]

Hello all.

I am just trying to figure out ways to inexpensively make a dent in our heating costs. We live in upstate NY (zone 4) with temps down to -20 at times in the winter. our house is gigantic and ooooold and a money pit. We have insulation in the attic and under the floors. Thats it. We cant insulate the walls due to costs and asbestos siding, not to mention all the freaking lath and plaster. Its a goal, but not feesible anytime soon.

ANYWAY, I was wondering- why cant we take some hosing and run it under our floors, where the insulation would cover it, and then attach it to one or more passive hot water heaters like this one ---> just a black insulated tank thing set it up with a small solar powered pump to cycle the water as it heats and cools. And some shut off valves to keep the cold night time water from chilling the house.

I dont understand much of this stuff yet, but it just seems like something like this ought to be possible to use during the day time hours. Probably would need some tweaking to keep the tank and pipes themselves from freezing over night.

What are you thoughts? Any links to similar systems?

 

[k0xxx]

You can, although it won't be very efficient.

A more efficient way would be to use metal piping that is soldered, or thermally bonded to a metal plate. The plate would sit against the floor, between the floor joists, and provide a much larger thermal surface area.

However, the method that you are suggesting would be relatively cheap and easy. For those reasons alone it might be worth trying just to see what the cost to benefit ratio might be. As for freeze protection, since it won't be a part of your potable water system, just add some antifreeze.

 

[Amosunknown]

i never thought of antifreeze for some lame reason.

Wouldnt any metal sheeting work for the purpose? Like recycled roof flashing or something? Its the metal thats holding the heat against the floor and distributing it more evening right? So any metal would work as long as its flat....

 

[noobiechickenlady]

MEN, Mother Earth News has lots of info about solar water, as well as the ever popular Build It Solar.
http://www.motherearthnews.com/search.aspx?search=solar water
http://www.builditsolar.com/Projects/WaterHeating/water_heating.htm

I've heard thin fibercement boards will increase the thermal mass if applied between the subfloor & the radiant floor pipes. Stands to reason as concrete is a thermal mass. They are fairly inexpensive.

There are as many options for solar hot water as there are people who use it, keep researching and you are sure to find a simple, cheap system that will work for you. Good luck!!

 

[k0xxx]

Yes, the flat metal is what transfers the heat to the floor. The problem is getting the heat from the hose to the metal. Only a small area of the hose is actually in contact with the metal, so there is a very large amount of heat loss.

Perhaps putting the hose between two pieces of metal, one that is flat, and one that has a ridge would provide more surface area for conducting heat. You could possibly use strips of ridged roofing tin for the bottom and flashing or the top. Below is an attempt to illustrate what I am talking about.

BTW, these are just some personal thoughts, I have no experience in actually doing this.

 

[Amosunknown]

Would there really be such a great loss since the joists are filled with 8 inches of insulation batting? The hose would at least be insulated from the basement by that....

 

[patandchickens]

ANYWAY, I was wondering- why cant we take some hosing and run it under our floors, where the insulation would cover it, and then attach it to one or more passive hot water heaters like this one

I kind of doubt you'd get much meaningful heat transfer through your floorboards. I think you'd mostly end up with mildly warm floor-insulation

You would also have to be AWFULLY sure of a) the quality of your plumbing, and b) the absolute freezeproofness of the entire assembly... because otherwise I see major water damage in your future, which in a plaster-and-lath interior is just an AWFUL mess

If you want solar supplementation, I wonder if you could do some sort of "popcan solar heater" type rig on the S side of your house (unfortunately it pretty much does need to be attached to the house, which if you are trying to maintain historical authenticity of appearance would be a problem... but if you could attach it even to a porch or mudroom entryway or such, that might not look too bad...). The kind of thing where you get some large panels of glass or Suntuf (plastic roofing rated for hi temps) and put dark-painted metal behind it, wiht just a narrow airspace, and house air feeds into the panel from the bottom, is heated by the sun, and rises thru a second hole into the house from the top of the panel.

I have a small greenhouseified chickenrun on the front of my chicken bldg that works like this (although it is not a popcan heater per se) and in late Jan or Feb can boost the temperature of the (insulated, but unheated and on bare slab) 15x40' building by 5-10 F during the day (!). (It doesn't work as well right around the winter solstice when the sun is lower, but it still does a lttle good then).

You do need a way to open/close the openings at the right times of day, and if it is cloudy (I would not trust the passive flaps used in warmer climates)... but it might really help you, at least on the sunward side of the house.

Good luck, have fun,

Pat