Seasonal storage insulation?

Hi everybody!

Well, getting out of the rocket stove corner for once. I plan on building my house/workshop one of thoses days. Post and beams, on concrete piers. Cos that's easy. This will be the the workshop level. I plan on insulating with strawbales rendered. Osb on the inside, since it's a workshop. First layer below the strawbales will be aerated autoclaved concrete blocks. May be two layers. It's in an artisanal estate, and they ask us to raise the floor level about 50cm above the original ground, due to flood risk. I was planning to put about 40 tons of gravel and a thin concrete slab above. I have been thinking about using this as a seasonal storage of some kind. May be puting the exhaust of a rocket through it. And water solar pannels heating this up too. On the perimeter, no prob, ytong blocks will insulate. But underneath, what can i use to avoid heat conduction into the ground? And what R value would be sensible?

Thanks a lot and best regards.

Max.

What area do you live in? Are you thinking of storing summer heat in that 40 tons of gravel to be used in the winter? I can put some numbers to this later when I get home.

Rl Workman wrote:What area do you live in? Are you thinking of storing summer heat in that 40 tons of gravel to be used in the winter? I can put some numbers to this later when I get home.

Hi RI workman. Thanks for the reply.

Well, i'd love to save at least a bit of that summer heat. I live in a French alps sunny spot.

5000 feet high, in France, but about ten miles from the Italian border, and about 160 miles from the mediteranean sea. With aproximately 300 days of sun per year (seems less now, than when i was younger) and about 20ft of snow on average. And an average temp of 7.7C° along the year. Sorry i don't have numbers for the sun radiation.

Hi Satamax, sounds like you live in a great location. Passive solar heating sounds like a sure thing in your location. As for "seasonal storage" I dont think this strategy has proven itself cost effective in any climate although I may be misunderstanding your intentions. Focus on good passive solar design, air-sealing and high R values.

Trying to get fancy with excessive thermal mass usually does not work because structures leaks too much air and bleed too much heat through windows and the building envelope to make it worthwhile.

Hi Brian.

Thanks a lot for your reply.


Well, high R values, i know how to do it. Latest stick framing building i did, a bedroom extension for a small house. I did R6.30 (euro rules) in the walls, and R8.15 for the roof. All sealed with inside heat reflective vapor barier. I'm a timber framer and roofer by trade. And, i'm pretty sure i can do a big heat storing mass for the workshop. I was calculating it yesterday, and i'm thinking about 48 metric tons of insulated gravel. Cost gonna be about 5000 dols. I'm up to par with rocket mass heaters now. Only thing i need to learn is solar heating.

Satamax, I agree with Brian, the focus should be on a well insulated design.
It sounds to me like you have to put this gravel in anyway so you are thinking about using it as a thermal reservoir. I did look into the solar radiation levels in your area and to store away enough summer heat for use during 3 months in the winter you would need nearly 8 square meters of solar collectors! (This is only 1400W too, a small space heater). From what I have read about insulating these thermal reservoirs you would need substantial insulation around the base and sides (~R75). Insulation on the top would also be required so that it doesn't heat the house during the summer. To heat during the winter a heat exchange system would be needed to circulate the heat up into the living space. Like Brian said this whole setup could get costly. If you decide against using that gravel as heat storage you may want to put some insulation between you and it so that you don't have a cold feet all winter

Hi Satamax, I have seen similar builds on a program called Grand Designs presented by Kevin Mcloud, some use cob, others use concrete but one thing you don't do is render/plaster walls etc as this decreases the thermal storage effect of the mass, Dave

Thanks a lot guys.

Well, seems like i'm heading another path. Trying to buy a place alrerady built.