Passive Solar/Thermal Mass Question

[JSeery]

I'm a newbie trying to heat a California designed house in NY. I've got the wood burning thing under control, but I'm looking for ways to retain more heat upstairs, which has cathedral ceilings and poor ceiling insulation. The roof is relatively new, but poorly done, so I figure I'll replace that insulation when I put a new roof on. But that is (hopefully) around 10 years from now, and I'm brainstorming about things I can do this winter.

Unfortunately, I have a wall of single pane glass facing north. I'm talking to an architect to see how I can deal with that. I also have a pretty good sized wall of single pane glass which faces south (see pictures). On a sunny winter day, this really heats up the southern side of this open floor space. The northern side gets heated by the wood stove.

I'm wondering whether it makes sense to harness some of this sun to help out with heating. In the pictures, there is a roughly 6' by 11' space above my pantry/laundry/half bath. The more central portion of this area gets really nice sun. Last spring, I used it as a sort of greenhouse to start a lot of seedlings for the garden.

But I'm thinking about ways to help retain heat with this area. I think an easy idea would be to create a poor man's trombe wall by just laying down some bricks up there in the hopes that they would heat up in the sun and release the heat overnight. But then I saw people online talking about water (or salt water) containers, so maybe I could put some large containers of water up there, for the same effect? Should said containers (or bricks) be painted black?

Are there any other options I should consider?

Anything I put up there will have to be lifted up to that space, so that is some limitation.

Thanks, in advance, for your advice.

 

[DougA]

I can give you my experience with mass storage and you can judge it with other replies. The theory and the practical are two different things.

I'm about 100 miles from you so very similar weather and sunshine. I have a south facing window wall of nearly 200 sq ft. in a great room of 900 sq ft with 10 to 17' cathedral ceilings. Insulated with R40, except the window wall, which is lowE argon filled sealed double glass. Basically, all sides well insulated, except one - that's my choice because we love the open view. We get a ton of sun in the winter on sunny days and it does heat the house very well (75+ deg) but only until the sun sets. Even though I designed the house with very high mass, in reality, it makes very little noticeable difference. The sun hits ceramic tile mortared onto a 5" cement slab with lots of insulation below it. It also hits a cinder block wall that is 20' x 5' high. That's many tons of mass storage and if it wasn't for the fact that the design of the walls is a wonderful architectural feature to the house, I would remove it because as heat storage, it's worthless.

What is good is that all the mass really helps to soften the highs and lows of temperatures. The house cools slowly and conversely, heats slowly. You still can easily tell when the sun is setting and the wood stove takes over for heating.

Back to your question. I would put a good quality fan on the ceiling and make sure the air gets circulated. Ours is on low in the evening and it creates enough movement to eliminate stratified air but not enough to feel any breeze. Your window wall facing north is sucking all you heat out. I can't overstate this enough! Adding insulation to the roof is pointless (wasted $$) unless you deal with all the heat going out the glass. Triple glazed with curtains on the north glass would be my suggestion. You will notice the difference instantly.

I don't think any mass you add to the upper area will make any difference at all. If you do it, it will only be a psychological improvement. The theory and stats say otherwise but I go from real world experience and in this case, science does not work out. I've had plenty of arguments with profs and Phd's and none of them lived in their own ideas, they just told other people what to do.

If you want to put tanks of water in the upper area, be sure to have an engineer check it. Water is VERY heavy and IMHO is not worth anything unless you hook it up to a circulation system that is connected to solar panels, just like a solar swimming pool heater. I re-read your post and not sure if the upper storage space is facing north or south. If it;s north, then adding the solar panels will probably not be aesthetically workable.

Bottom line to me is that the glass wall is horrible for heat but amazing for view and personal well being. My wood stove makes up for the heat loss and any further additions of mass to me, is wasted money.

 

[semipro]

Firstly, I suggest you spend some time at builditsolar.com. The site has lots of info on the issues you're dealing with including the benefits of thermal mass in sun spaces, window insulating, etc.
I second Doug concerns about window heat loss and the weight of any thermal mass you install. Consider also that any heat you store up there will leave via the same windows it came in once the sun goes down.
If you're set on trying something up there perhaps a dark ceramic tile might work. You wouldn't even have to set it in mortar.
In general though, it would be better to let the heat in when its sunny, trapping it inside by closing the shades when it gets dark.

 

[JSeery]

I can give you my experience with mass storage and you can judge it with other replies. The theory and the practical are two different things.

I'm about 100 miles from you so very similar weather and sunshine. I have a south facing window wall of nearly 200 sq ft. in a great room of 900 sq ft with 10 to 17' cathedral ceilings. Insulated with R40, except the window wall, which is lowE argon filled sealed double glass. Basically, all sides well insulated, except one - that's my choice because we love the open view. We get a ton of sun in the winter on sunny days and it does heat the house very well (75+ deg) but only until the sun sets. Even though I designed the house with very high mass, in reality, it makes very little noticeable difference. The sun hits ceramic tile mortared onto a 5" cement slab with lots of insulation below it. It also hits a cinder block wall that is 20' x 5' high. That's many tons of mass storage and if it wasn't for the fact that the design of the walls is a wonderful architectural feature to the house, I would remove it because as heat storage, it's worthless.

What is good is that all the mass really helps to soften the highs and lows of temperatures. The house cools slowly and conversely, heats slowly. You still can easily tell when the sun is setting and the wood stove takes over for heating.

Back to your question. I would put a good quality fan on the ceiling and make sure the air gets circulated. Ours is on low in the evening and it creates enough movement to eliminate stratified air but not enough to feel any breeze. Your window wall facing north is sucking all you heat out. I can't overstate this enough! Adding insulation to the roof is pointless (wasted $$) unless you deal with all the heat going out the glass. Triple glazed with curtains on the north glass would be my suggestion. You will notice the difference instantly.

I don't think any mass you add to the upper area will make any difference at all. If you do it, it will only be a psychological improvement. The theory and stats say otherwise but I go from real world experience and in this case, science does not work out. I've had plenty of arguments with profs and Phd's and none of them lived in their own ideas, they just told other people what to do.

If you want to put tanks of water in the upper area, be sure to have an engineer check it. Water is VERY heavy and IMHO is not worth anything unless you hook it up to a circulation system that is connected to solar panels, just like a solar swimming pool heater. I re-read your post and not sure if the upper storage space is facing north or south. If it;s north, then adding the solar panels will probably not be aesthetically workable.

Bottom line to me is that the glass wall is horrible for heat but amazing for view and personal well being. My wood stove makes up for the heat loss and any further additions of mass to me, is wasted money.

Thanks for the input on this. In answer to your question, the upper storage space is on the southern end of my house, so the pictures were taken facing south. We have 3 ceiling fans in the upper level, and they do help out a good deal on the winter setting. In the summer, I pretty much solely use those and barely ever turn on the A/C. That's the flip side to vaulted ceilings, I guess.

I totally agree regarding the north wall. I'm actually going to get rid of most of that glass. I will leave a double or triple glazed picture window because the view of the woods is very pretty, but will cut WAY down on the total glass surface area, and make sure the new north wall is insulated well. The other problem area is the western wall. That has 5 vintage (1965) sliding glass doors on it, only 2 of which work. All of them leak. To make matters worse, I live half way down the eastern slope of a steep hill, so my solar gain from that side is pretty much nil. Those are getting replaced as soon as I can afford it. Again, a couple of those might just become a wall because who needs five doors in that small of a space. This ain't California.

I appreciate the candid advice re putting some mass up there. I might experiment with some bricks or jugs of water just for fun, but will definitely avoid spending any $ on this.

 

[JSeery]

Firstly, I suggest you spend some time at builditsolar.com. The site has lots of info on the issues you're dealing with including the benefits of thermal mass in sun spaces, window insulating, etc.
I second Doug concerns about window heat loss and the weight of any thermal mass you install. Consider also that any heat you store up there will leave via the same windows it came in once the sun goes down.
If you're set on trying something up there perhaps a dark ceramic tile might work. You wouldn't even have to set it in mortar.
In general though, it would be better to let the heat in when its sunny, trapping it inside by closing the shades when it gets dark.

Thanks, I'll check out that site. And I'll put shades/curtains on the list.

 

[Circus]

Before thinking solar or thermal mass, first stop hemorrhaging heat out those single glazed windows. Install another layer using perhaps plexiglass sheets. It's easy, cheap, attractive (not too ugly) and now. There's kits available.

 

[JSeery]

Before thinking solar or thermal mass, first stop hemorrhaging heat out those single glazed windows. Install another layer using perhaps plexiglass sheets. It's easy, cheap, attractive (not too ugly) and now. There's kits available.

Thanks. I definitely agree that the single pane glass is my biggest problem. Would you recommend magnetic storm windows on the inside? That seems like a pretty good solution to at least some of my windows (those I am not eliminating), and should be pretty cheap. Any reason not to use those, rather than replacing with much more expensive double pane glass?

 

[DougA]

Any reason not to use those,

Sometimes the glass will fog up unless you are using sealed units. There is also film kits that you can tape the edges, roll the window film on, then use a blow dryer to shrink fit the film so it's almost invisible. That would be a better seal and very cheap until you get proper glass. For the north facing side, I would triple glaze. Double glazed sealed units will still be cold to the touch, triple almost eliminates that.

 

[Circus]

should be pretty cheap. Any reason not to use those, rather than replacing with much more expensive double pane glass?

Can't think of any. Odd shaped thermopanes cost a fortune.

 

[peakbagger]

I had some experience with the plexglass double pane windows held in with magnets on vinyl strips on my parents former home. They did make a difference but the plexiglass got cloudy over the years (almost all plastics do in sunlight).There was some distortion visible when new and over the years it was more noticeable . The strips were attached with self stick tape and the adhesive would let loose on occasion on sunny days. The windows were 10 feet off the floor so when they fell down, it was quite dramatic. We didn't have any significant fogging issues. Overall a plus but it definitely not perfect

 

[woodgeek]

Hate to say it but you have two problems. All that single pane glass is a huge heat leak. The second problem is that your thinking about solar heating is a bit too optimistic for your climate and region. South facing, single pane glass is barely break-even on heat BTUs where you are, IF there is no shading and decent wind protection. IF you have branch shading, you are still a net loss on the south side at R-1.

Bottom line, you bought a house with a really nice aesthetic feature: glass walls in two directions, giving nice views and daylighting. But that feature comes with a cost, an annual heating bill of roughly $2-3/sq ft of that glass. If we are talking 200 sq ft of glass, you're on the hook for ~$500/yr for your beautiful house feature (not counting wood heat).

So, do you and your family enjoy that aspect of your house? You bought the place for a reason.

I don't think you should do anything (more) on the solar/storage front, unless you are overheating sometimes now. Then I would think about adding shading overhangs on the south, that wouldn't kill your winter gains too much. Storage is a losing game (given how small your winter gain is) and unattractive. You don't want to intentionally destroy an architectural feature of your house...it might be penny wise-pound foolish. You might save $100-200/yr for the next 10 years, and then at resale you will lose the rich guy who wanted your house as it is now, for whom the $500/yr is a reasonable cost for a nice architectural house for entertaining clients, etc. Instead you might sell a mishmash remodel at a (relative) loss.

There are things you can do to make the situation more efficient, and save some of that $500/year. All would be very expensive. Replacing the glass for R-3 low-e double pane would do the trick, but then has a lifespan issue...prob 20-30yrs for the sealed units. Will saving $400/yr pay for the replacement, and then again in 30 years from now? Probably not, but my guess is they would make the space more comfortable in the winter (by reducing radiant coolth).

In summary, when frugal people buy expensive, architectural homes they are often unhappy and do weird things to them. This misses the point, and seldom saves money. I think you should ONLY make changes that (1) you can afford (2) make the house more comfortable (3) preserve its architectural quality, and then either way learn to be happy with your unique house. If you can't do the last bit, you should just move.

 

[JSeery]

Hate to say it but you have two problems. All that single pane glass is a huge heat leak. The second problem is that your thinking about solar heating is a bit too optimistic for your climate and region. South facing, single pane glass is barely break-even on heat BTUs where you are, IF there is no shading and decent wind protection. IF you have branch shading, you are still a net loss on the south side at R-1.

Bottom line, you bought a house with a really nice aesthetic feature: glass walls in two directions, giving nice views and daylighting. But that feature comes with a cost, an annual heating bill of roughly $2-3/sq ft of that glass. If we are talking 200 sq ft of glass, you're on the hook for ~$500/yr for your beautiful house feature (not counting wood heat).

So, do you and your family enjoy that aspect of your house? You bought the place for a reason.

I don't think you should do anything (more) on the solar/storage front, unless you are overheating sometimes now. Then I would think about adding shading overhangs on the south, that wouldn't kill your winter gains too much. Storage is a losing game (given how small your winter gain is) and unattractive. You don't want to intentionally destroy an architectural feature of your house...it might be penny wise-pound foolish. You might save $100-200/yr for the next 10 years, and then at resale you will lose the rich guy who wanted your house as it is now, for whom the $500/yr is a reasonable cost for a nice architectural house for entertaining clients, etc. Instead you might sell a mishmash remodel at a (relative) loss.

There are things you can do to make the situation more efficient, and save some of that $500/year. All would be very expensive. Replacing the glass for R-3 low-e double pane would do the trick, but then has a lifespan issue...prob 20-30yrs for the sealed units. Will saving $400/yr pay for the replacement, and then again in 30 years from now? Probably not, but my guess is they would make the space more comfortable in the winter (by reducing radiant coolth).

In summary, when frugal people buy expensive, architectural homes they are often unhappy and do weird things to them. This misses the point, and seldom saves money. I think you should ONLY make changes that (1) you can afford (2) make the house more comfortable (3) preserve its architectural quality, and then either way learn to be happy with your unique house. If you can't do the last bit, you should just move.

All very good points, and things I will keep in mind as I renovate. Thanks for the input.

 

[semipro]

In summary, when frugal people buy expensive, architectural homes they are often unhappy and do weird things to them

So true. I'm living that life.

Then I would think about adding shading overhangs on the south, that wouldn't kill your winter gains too much.

I came across this related discussion recently at Greenbuilding Advisor:

"Overhangs to shade south-facing windows are ugly, unnecessary, and counterproductive
You don’t need them. The theory is that overhangs should be designed to provide full shading of the south-facing glass in the summer and no shading in the winter. Part of the problem is that most of the standard summer designs for these overhangs are based on June 21 at noon. Unfortunately, this is neither the hottest time of day nor of the summer.Likewise, winter designs are usually based on achieving no shading on December 21, which is certainly not the coldest day of the winter.In my experience, these overhangs are not really needed. Because of the high solar altitude in the summer, over half of the solar radiation striking the glass is simply reflected away; another significant fraction of the solar radiation is rejected by the glass coatings.Most overheating problems in the summer are due to east and west windows — window which can’t easily be shaded and which obviously should be minimized in the design."
Read more: http://www.greenbuildingadvisor.com...arian-view-passive-solar-design#ixzz3q3ixxtNS​

 

[begreen]

Instead of overhangs I like grape arbors designed into the look of the house. Cool shade and fruit too.

 

[DougA]

"Overhangs to shade south-facing windows are ugly, unnecessary, and counterproductive

WOW, I disagree 100% with that. We are both at a similar latitude and the shading on our south facing window wall is critical. We get zero sun in mid summer from 11 to 2 and just a small amount of sun hits our floor until late in the afternoon. Mid-season (right now) the sun hits almost the entire 10' depth of our sun room. Mid-winter, the sun hits the back wall, which is 24' from the windows and 5' up. It is impossible to believe unless you see it yourself.

The heat from the sun is far greater than my wood stove can put out, which is rated at 120K BTU. The other thing that most people don't calculate in is the sun vs. overcast. We get a lot of high pressure (sunny) days in the winter and a lot of overcast/rain in the spring & fall. Today it's cold outside and the room is mid 70's with no heat, other than the sun.

In more southern latitudes, it may be quite different. My house was specifically designed for solar heat in the winter. Even before we moved in, I planted a Shademaster Locust 10' from the front of the glass. It was 10 yrs before the tree made a huge difference but now we rarely use a/c in the house.

To clarify something woodgeek said about lifespan. We built 32 yrs. ago and all of the original sealed glass units have been replaced, most under warranty and most, multiple times. Those units had problems from day one due to terrible design. They would snap crackle and pop every time the sun came out in the winter and every time it got cold at night. We had foggy glass, cracked glass and constant dripping from condensation. The new units are low E, argon filled and have been in 15 yrs. and have been awesome. Zero problems, zero snapping, almost no condensation. They are expensive yes. In my case, I had to go with stronger aluminum frames because they are large and needed to be wind proof. Now, almost everything is vinyl or fiberglass and as strong as the aluminum I bought but MUCH cheaper. I expect mine to last well past 30 yrs. and probably 50+ although I won't last that long to prove it to you.

If you go to a place that manufactures sealed units, the price is cheap. I've replaced all the windows in my son's century old house and I was shocked how cheap they were. We've got 4 window mfg. near us, so maybe the competition is forcing the price down. Don't go to a glass store unless you need to have them do the install.

 

[peakbagger]

I do agree that overhangs make a difference with summertime overheating. Long ago I installed a solar array over an angle bay window. Its has an adjustable tilt. The net result is it shade the angle bay quite nicely. It was quite noticeable the first year and subsequent years that the interior of my house is lot cooler in the summer. When I set the array to the winter angle, it allows the light in with low sun angle so I still get winter heat.

 

[woodgeek]

I think people make too much of overhangs AND passive solar heat (in the Northeast climate zone). I would say that overhangs could help IF there is an overheating issue. That is, my take is that a lot of these decisions should be about comfort. The OP wouldn't replace the glass the save $400/yr, but might if the space gets more comfortable and thus usable. My guess is that those spaces are great Spring-Summer-Fall, and the south room is nice in the winter on sunny days, but otherwise in Winter both glass spaces are uncomfortable with big single panes. My guess the wood stove on the N side is there to provide enough radiant heat to make the space usable in the winter.
If the OP finds the spaces not as useful as hoped during cold weather, then he could invest in radiant space heaters or better insulated glass, depending on budget.

Case in point: I had a single pane picture window in my south-facing, eat-in kitchen. The daylighting in there is very attractive, people are drawn to the space, but it was always cold trying to sit at that window. I got a fixed low-e storm window added over the outside of the existing single-pane, maybe $250, and the comfort difference is astounding. Its a blast to sit there in January on a sunny day having a coffee, or during a blizzard watching the snow fly, but cozy.