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Old 03-22-12, 11:29 PM   #1
roflwaffle
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Default I'm looking for advice on a new home.

I'm within a week of closing on a really neat/odd home and I wanted some input on weatherizing it. The climate is Mediterranean, so that's a plus.

It's a two story house, and the bottom level is masonry that's earth-bermed on two sides (the north and the west). It also has some pretty big windows facing east. The top level is stick that's exposed on all sides, but it also has R20 fiberglass insulation and concrete tiles.

The upper level seems like it's pretty well insulated, but the lower level has crap for insulation because th R-value for masonry seems to be really low. Otoh, being built into a mountain it also has a ton of thermal mass, on top of whatever is gained via the concrete walls.

I've been searching for info, and from what I've seen it looks like it's best to insulate the exposed masonry, but the I've also read that there's less need to insulate anything earth-bermed since it will tend to stay pretty consistent in terms of temperature. Does anyone have any experience/input with this kind of house? It seems really unique so I'm not sure where to even start.

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Old 03-23-12, 12:29 AM   #2
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Quote:
Originally Posted by roflwaffle View Post
I've been searching for info, and from what I've seen it looks like it's best to insulate the exposed masonry, but the I've also read that there's less need to insulate anything earth-bermed since it will tend to stay pretty consistent in terms of temperature. Does anyone have any experience/input with this kind of house? It seems really unique so I'm not sure where to even start.
Unless the mean annualized temperature of the ground surrounding your basement is at or above the temperature you find comfortable in your living environment, you're going to be losing heat from your basement out into the berm. The insulation on the basement walls will slow the heat transfer.

If I were in your shoes, I'd be seriously inclined towards insulation but I'd double check myself on the economics of the renovation. How much is spent on heating the home, how much of the basement is used as livable space, how much will it cost to insulate and what would the payback period be.

You say that it's in a Mediterranean climate so I think that makes the proposition a bit more iffy than if you lived in Alaska.
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Old 03-23-12, 02:58 AM   #3
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at my old house I had a shop 12'x24' with the long back buried in a hill with 2' of stick sticking up and 8' of concrete buried. The sides were partially bermed as it sloped down.

I didn't bother to insulate the concrete at all. I'm going to guess that the ground temperature was about 9C in winter to 14C in summer because the temperature inside never moved out of that range if the door and windows were kept closed. One day it hit 29C outside in the shade and I had left all the windows and the door of the shop open for a few days. Inside hit 16C. When I closed it up temps came back down. In the winter I used a small space heater aimed right at me. It would have been near impossible to heat the building up enough to be comfortable.
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Old 03-23-12, 11:36 AM   #4
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Default Aim ahead of the duck, if you want dinner...

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I'm within a week of closing on a really neat/odd home and I wanted some input on weatherizing it. The climate is Mediterranean, so that's a plus.
roflwaffle,

It would be really helpful if you said something about the geographical location and elevation and solar orientation of your home.

"Mediterranean" can have a very broad meaning.

In Portland, Oregon (my fair city) the city planners are calling Portland a Mediterranean climate (possibly to enhance the touristic value), but EcoRenovator is getting postings from folks near the Spainish Mediterranean coast. Now THAT is clearly Mediterranean.

Also, there is good reason to believe that the rapid increase in energy costs is not an anomaly, and is likely to increase. This will mean that not only fuel will get more expensive (this includes electricity), but also that anything that requires industrial processing will also get more expensive (this includes insulation).

My house, for instance, was built in 1892, at a time when forests were assumed to be inexhaustible and firewood was essentially free. During that time, insulating your home would be absurd, so it was not insulated.

But now, the forests are not inexhaustible and heating energy is far from free and insulation is a necessity. So what I'm trying to say is that you have a moving target. As every duck hunter knows, you don't shoot at the duck, you aim ahead of the duck, if you want dinner.


From the above chart, you can see for yourself that the duck is flying pretty fast. Aim ahead of the duck, if you want dinner.

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Old 03-23-12, 02:42 PM   #5
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I've seen a couple papers (Here's one indicating that something with concrete on the inside and insulation on the outside with a R-value of about 15 would have a DRE of about 40) on how much less energy a home using a lot of interior thermal mass can use compared to traditional home designs with the same R-value.

Along those lines putting external insulation is a great idea. Going from R10 to almost R40 for a few hundred bucks is a definite win. That said I haven't found anything on the effects of interior insulation on earth-bermed structures. Does anyone have any non-anecdotal information on that? I'm guessing the average in-ground temperature is something like 60F during the winter, although that should swing by about ten degrees.
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Old 03-23-12, 04:11 PM   #6
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Does anyone have any non-anecdotal information on that?
So, you are looking for precise, useful information?

Quote:
Originally Posted by roflwaffle View Post
I'm guessing the average in-ground temperature is something like 60F during the winter, although that should swing by about ten degrees.
What are you basing your 'guess' on?

Sounds like you are preparing to spend "a few hundred bucks" which might go higher. I just re-insulated a wall in my kitchen, so I know that it might go higher.

It might be useful and cheap for you to get closer than 'guess' if you're actually looking for non-anecdotal information.

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Old 03-23-12, 05:14 PM   #7
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I'm looking for accurate generalizations. It doesn't have to be perfect, but I'm not sure if an anecdote will be very useful. I'm basing the earth temperature off of the average winter temperature/humidity for the region and graphics like this one.


The exterior walls are going to be more expensive to insulate (and make it look like the rest of the house due to the pine exterior), but there's also a bigger difference in heat loss and it's easier to constructively insulate them (insulation on the outside and thermal mass on the inside is best according to MIT.), but at the same time, it should be a whole lot cheaper to frame/insulate/drywall/paint the interior than it will be to frame/insulate/sheath/paint the exterior, but the returns will also be lower because the ground will be warmer than the exterior during the winter, and it's the most ineffective combo of thermal mass/insulation.

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Old 03-23-12, 05:48 PM   #8
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Quote:
Originally Posted by roflwaffle View Post
(insulation on the outside and thermal mass on the inside is best according to MIT.), but at the same time, it should be a whole lot cheaper to frame/insulate/drywall/paint the interior than it will be to frame/insulate/sheath/paint the exterior, but the returns will also be lower because the ground will be warmer than the exterior during the winter, and it's the most ineffective combo of thermal mass/insulation.

What is "best?"

It looks to me like you have to do an optimization calculation here. There is clearly a Best standard for minimizing energy usage, a best standard for retaining heat in the thermal mass, a best standard for use of your money, a best standard for ease of construction.

If you have a clearly defined objective then the calculation should be easy, for instance, if your prime objective is to take the path which leads to the lowest expense, then insulate the inside, and don't worry about how this results in a marginal decrease in the performance on the other metrics.

If however you are intent on finding the "just right" balance between all of these competing standards, then you're going to have to dig up a lot of info, do a lot of calculations and see if you can find a path to a solution which gives you a bit of everything so that it makes sense to you.

I don't think that anyone here can give you a clear cut answer until we know exactly what you want to achieve.
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Old 03-23-12, 06:08 PM   #9
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Read the paper Alan. The "best" is the combination of materials, in equal parts, that yields the greatest DRE. That's assuming the construction costs of each will be the same.

I'm asking for input on heat losses, which I need before I can do any calculations about what kind/how much insulation will be cost effective.
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Old 03-23-12, 07:03 PM   #10
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Read the paper Alan. The "best" is the combination of materials, in equal parts, that yields the greatest DRE. That's assuming the construction costs of each will be the same.
My question is in the same vein as "what is the best flavor of ice cream?" The answer depends on how you define best. The research you cite had some specific questions that they wanted answered. Are you saying that your criteria is a perfect match to their criteria, therefore their "best" is also your "best."

Also, I didn't see any mention of your undefined acronym DRE in that paper.

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