# Low Thermal Mass Sunspaces for Space Heating etc.



## SolarGary (Sep 8, 2005)

Hi,
I've been working on low thermal mass sunspaces the last couple months and have been really impressed with how well they do on space heating -- the tests indicated that they produce as much heat per sqft of glazing as a high quality commercial collector -- and, you can be in your collector reading the paper and having a cup of coffee while its collecting.

It seems like the combination of a really efficient collector along with all the things you can use the sunspace space for is a real winner.

http://www.builditsolar.com/Projects/Sunspace/sunspaces.htm#LowMassSS

What do you think?

Gary


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## Roadking (Oct 8, 2009)

Very interseting Gary. BTW, I've used your site for several projects, and this one falls into something I'm planning on this year.
Thank you!

Matt


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## SolarGary (Sep 8, 2005)

Roadking said:


> Very interseting Gary. BTW, I've used your site for several projects, and this one falls into something I'm planning on this year.
> Thank you!
> 
> Matt


Your welcome -- would like to hear how your project goes.

Gary


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## woodsy (Oct 13, 2008)

Hi Gary
Thanks for the informative post on Low thermal mass sun spaces.

I can see where this concept would benefit homes or shops with little south 
glazing especially and for not much investment . 
A great source of daytime heat
when the sun shines.
I could use something like this on my south facing garage/workshop that doesn't have a lot of glazing.

We are thoroughly enjoying our solar water heater design from you and your site
going on 4 years ago almost. Bought and payed for itself after only 2 1/2 years.
Big savings on our light bill for years to come!
Thanks for what you do 
with Build it Solar, will be looking at this LMT sun space some more.


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## Roadking (Oct 8, 2009)

Just added a 4'x12' porch to our south facing mudroom. Mudroom has 2 windows and 6 pane glass door, and absorbs a good deal of heat. I am planning on making a removable sunspace/green house for this porch, that ties into the house, so windows and doors can be opened/closed and the heat circulated thru the house. 
Probably won't get to it until spring...it's currently 11 degrees and windy as all heck.

Matt


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## SolarGary (Sep 8, 2005)

woodsy said:


> Hi Gary
> Thanks for the informative post on Low thermal mass sun spaces.
> 
> I can see where this concept would benefit homes or shops with little south
> ...



Hi Woodsy,
Great to hear the water heater is working well.

Have to say that working on the low thermal mass sunspace as a house heater and multipurpose space, I went from being a bit skeptical to being a real fan of the idea. I just can't think of any solar project that pays off so well in dollars and also has all the side uses.
Would like to hear what you think once you get a chance to read through it.


Gary


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## SolarGary (Sep 8, 2005)

Roadking said:


> Just added a 4'x12' porch to our south facing mudroom. Mudroom has 2 windows and 6 pane glass door, and absorbs a good deal of heat. I am planning on making a removable sunspace/green house for this porch, that ties into the house, so windows and doors can be opened/closed and the heat circulated thru the house.
> Probably won't get to it until spring...it's currently 11 degrees and windy as all heck.
> 
> Matt


We are at a balmy 40F in Bozeman -- feels like Spring.

Sounds like a good plan.
One thing to think about is to keep a lot of the incoming solar from being absorbed they the floor of the add on sunspace -- this is lost heat and can make a big difference in performance. Since its removable, maybe something like a layer of black weed cloth or shade cloth a couple inches of the floor?

Please post how it works out.

Gary


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## Roadking (Oct 8, 2009)

The deck is toung and groove Azex (trex type) material on a 2x10 floating frame that I filled with sand because I had been planning this from the start. The sand is to prevent draft, add insulation, and provide some solar mass. A work in progress.

And again, your site is a wealth of info.

Matt


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## woodsy (Oct 13, 2008)

SolarGary said:


> Hi Woodsy,
> lGreat to hear the water heater is working well.
> 
> Have to say that working on the low thermal mass sunspace as a house heater and multipurpose space, I went from being a bit skeptical to being a real fan of the idea. I just can't think of any solar project that pays off so well in dollars and aso has all the side uses.
> ...


Got to look over some of your construction details and performance data
and have to say nice job as always ! 
We already have the passive solar home working nicely for us but this
is giving me some ideas on the south wall shop addition i've been looking into.
Your costs seem to add up to about $10 per sq ft of floor (20'x 10' ?) space which is pretty reasonable giving the quality of construction and materials. 

As you state such a sun space could be multiple use and a greenhouse for starting veges early is part of my plan , along with heating the space in the shop and drying clothes sounds good too, storage etc..

My project would be 28' long by 8' wide and have about 10-12' of height to work with on that south wall so similar in floor area to your design.
I may want some thermal mass floor in the greenhouse section to moderate temps overnight. 
Do you think the double glazing is worth the extra cost for insulating value ?
Had single glazed polycarbonate like i used on my solar panels in mind.

I've been sold on solar heated spaces for 30 +years now and this concept
could have heating cost savings for a lot of homes which have little solar gain due to lack of windows and for reasonable prices.

In this day and age of high energy heating costs you would think there would be something in building codes mandating optimum use of the sun to heat water and living spaces. (where applicable) 

Thinking about waiting till spring to get started , snow cover and cold has set in hard here :thumb:


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## SolarGary (Sep 8, 2005)

woodsy said:


> Got to look over some of your construction details and performance data
> and have to say nice job as always !
> We already have the passive solar home working nicely for us but this
> is giving me some ideas on the south wall shop addition i've been looking into.
> ...


Hi Woodsy,

I do think that the double glazing pays its way.
In the greenhouse part, It would nearly double the heat loss for the greenhouse to use single instead of double, and it would be hard to put enough mass in to keep the greenhouse warm enough at night for the plants. 

I really like this all season greenhouse -- mine is basically a smaller version of it: http://aes.missouri.edu/swcenter/research/Solar-heated greenhouse.pdf
They talk about double glazing, and how its pretty much needed for a greenhouse that's going to go through the winter without supplementary heat. They use the two layers of poly with a small blower to inflate the space between for their double glazing.

But, if you don't plan to use the greenhouse all the way through the winter, then the single glazed could be used for a season extender, and during mid winter when its too cold to keep using it as a GH, it could contribute to space heating.

For the part that is not GH, but is a low mass sunspace that provides heat to the house during the day and goes cold at night, the single vs double is just a matter of efficiency -- the single would work fine, but not produce as much heat as the double glazed one. The difference is basically that since the sunspace goes cold at night anyway, you don't care about the night heat loss as you would on the GH.

If you don't need a view out the glazing, the twinwall polycarbonate goes for around $2 per sqft -- not a lot more than the corrugated SunTuf has crept up to. Its also very nice to work with, and you don't have to buy the end closeouts for the corrugations. The trick is finding a good source for it in your area -- one where the shipping does not eat you up.
Not that it helps much for where you are, but this is the place I order from:
http://www.greenhouses-etc.net/glazing/twinwall.htm



Gary


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## woodsy (Oct 13, 2008)

Hi Gary,
Nice breakdown on the single vs. double glazing.

Looks like a fun and simple project . 

When it comes together i'll submit the details with pictures to Build it Solar.

Thanks for the great info !


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