To insulate or not?

[Woodboy]

Working on basement shop, two interior walls are completely underground with earth on the entire other side of the walls. I plan to insulate the exterior "outside" garden level walls and the ceiling for sound reasons, but the question is should I insulate the under ground walls. I would like to use construction adhesive on those walls and in addition to the extra cost of unnecessary batt insulation, if I use a poly vapor barrier, I can't apply adhesive between the dry wall and studs.

The ceiling will be suspended ceiling tiles with batt insulation above, clearly nothing insulates for temperature like 50 feet of dirt, but I wonder if I'll gain much sound deadening by adding a little fiberglass insulation in those walls. Upstairs is living space.

Thoughts?

[Knottscott]

For the underground walls I would insulate to at least the frost line in your area. The savings should come back to you in a couple of years.

[jackellis]

We're building a house at Lake Tahoe where the weather is probably a bit colder and I've been obsessing over how to make the house (with a shop) as energy efficient as possible. To start with, there will be 2 inches of "blue board" underneath the whole slab, and insulation inside all of the stem walls.

I agree with Dustmight. Whatever source you use for heating isn't going to get cheaper over the long run and it is a lot less expensive to insulate at the beginning than to retrofit later.

Also...I would use either spray foam or sprayed-in fiberglass. IMHO fiberglass batts are a waste of money, especially in really warm or realy cold climates, unless you take a lot of care to install them very carefully with no gaps or wrinkles, correct side facing in, etc. The sprayed-in products pretty much have to be professionally installed but you'll be more comfortable and spend less money on heat.

Also...make sure you seal cracks in the framing carefully. Air leaks will cost you lots of heating $$. We had a professional run numbers for us and by making the house super tight, we'll be able to use a smaller heating plant and probably cut our heating bills by 25-30%.

[dbhost]

While I am no expert in cold climates, I can tell you after living in HOT climates for decades, and working and living with Engineers of all sorts, the laws of thermodynamics and economics are pretty straight forward. Energy (heat) cannot be created nor destroyed, but simply moved. The cold cold earth on the other side of that basement wall will be sucking the heat from the air via 3 methods.

#1. Convection.
#2. Conduction.
#3. Radiation.

Boiled down to soup & nuts... Convection is movement of heated molecules through a liquid or gas, so heated air, via convection will rise, cooled air will fall. If I understand the process properly, a colder body will attract the warmer molecules, so the cold concrete wall will attract the warm air molecules to get to the next little trick, Conduction. Meaning transfer of the energy, in this case thermal energy (heat) from the hot body (air) to the cold one (cement wall) via contact. And finally Radiation, is movement of energy (heat) even in vacum with no means of convection or conduction. This is most often percieved as visible light. (and why the Sun heats our cozy little planet).

You will not be able to completely stop the processes, but you WILL be able to slow them down...

Insulating batts, blow in foam, etc... works, because it SLOWS the movement of the liquid or gas to a near standstill, thus dramatically slowing the processes of convection, and conduction. The thicker the insulation the more slowing effect is produced. And which is also why 2x6 stud walls are able to carry a higher R value rating than 2x4 walls.

Another MUST DO for insulation is to SEAL any, and all air leaks. You need to get busy with the caulk, and if you have any electrical outlets or similar on the exterior walls, you will need to use the outlet cover gaskets carried in hardware stores... And caulk up the gaps between the studs and the exterior wall. The idea here is to slow down or stop air movement...

Radiant heat barriers, are typically reflective material, between the insulating material, and the environment being insulated from. So in roofing, it would be on the bottom of the roof decking, or in some designs, suspended from the rafters just below the decking, with an air gap feeding a ridge vent... Reflectix is a popular product for that particular application. There are also reflective coatings that do the same general thing...

The whole idea is to "bounce" the energy (heat) back where it came from. I have never seen it installed this way, but thermally speaking, I would think a radiant barrier working to keep heat IN would be most effective mounted just inside the sheet rock. Obviously that won't pan out well though...

Substantial energy savings can be realized by sealing and insulating properly, but yes, there are initial costs involved. So let's talk about financial realities about this....

#1. It is FAR cheaper to insulate in the build process, than to go back afterwards.
#2. Energy costs are only going to go UP.
#3. The more energy (fuel) we can conserve, the slower the raise in energy costs.
#4. Your equipment in an environmentally controlled shop, with good insulation, and humidity control will resist corrosion, and failure FAR longer. Even buying second hand, or cheaper brand equipment, a well equipped shop can EASILY have $10,000.00 in equipment to be protected.
#5. Likewise for the not so cheap lumber. Keeping temps stable, and humidity low, will help avoid warpage...

Hope this helps you make up your mind. Honestly I hope you decide to insulate. I am busting my behind to get that done, but a little bit of a blowhard came through and messed my plans up a bit...

[TheRic]

I agree with the previous posts, and I'll add that it's a good ideal to insulate since concrete has an R value of something like 0.001. In other words a plastic cup / bottle has a better R value than several inches of concrete. Have you seen moisture on the outside of a plastic cup / bottle. Same thing will happen. Then it will be behind closed walls, no light. Moisture, Dark.....can you say MOLD.

I will admit that is an extreme and I am simplifying things, but I would strongly suggest to insulate to at least just below the frost line if not more. I insulated my basement office only to the frost line at my brothers suggestion, was trying to save some money. I which I would have spent the extra money and gone down the extra 3'. The cold / heat can now escape from the uninsulated section up behind the insulation.

[gjat]

I just don't understand these Yankee rooms below ground and what they do with them. In Florida, we fill them with water and call them pools. No need to insulate at all.

[dbhost]

No doubt. Actually, my Cousin used to own a little house in Oregon by OSU that had one of those fancy under house rooms and due to a plumbing problem, it ended up requiring the judicious application of a couple of sump pumps... And swim fins...

[Kristofor]

Also...make sure you seal cracks in the framing carefully. Air leaks will cost you lots of heating $$. We had a professional run numbers for us and by making the house super tight, we'll be able to use a smaller heating plant and probably cut our heating bills by 25-30%.

I wouldn't argue against the wisdom of insulating, as I don't know that I've ever seen a conflicting opinion from an expert. And in fact my whole basement is insulated even the below ground areas.

That said, even living in Minnesota I pay much more for the energy needed for cooling in the summer (trees are still fairly small, so no shade on the house) than I do for heating in the winter. So, while there would still be condensation issues, etc. I think the net impact for me it may have made sense to leave those walls unfinished to act as a heatsink in the summer, and take the relatively smaller hit on extra heating in the winter.

Clearly I'm missing something in that analysis as I've never heard any professional make similar statements, but it "feels" right...

Kristofor.

[dbhost]

I wouldn't argue against the wisdom of insulating, as I don't know that I've ever seen a conflicting opinion from an expert. And in fact my whole basement is insulated even the below ground areas.

That said, even living in Minnesota I pay much more for the energy needed for cooling in the summer (trees are still fairly small, so no shade on the house) than I do for heating in the winter. So, while there would still be condensation issues, etc. I think the net impact for me it may have made sense to leave those walls unfinished to act as a heatsink in the summer, and take the relatively smaller hit on extra heating in the winter.

Clearly I'm missing something in that analysis as I've never heard any professional make similar statements, but it "feels" right...

Kristofor.

Using the basement as a heat sink? Now there's an interesting concept! If the differential between ground temps, and interior temps is sufficient to provide a cooling effect during the hotter months, it might be worth it, but the basement would be a miserable place to be in the winter then.

I could stand some correction here, but I would think that the majority of your heat gain is going to be through the attic, and the windows. Low -e glass insulated windows, and packing more insulation, adding a radiant barrier to the roof would go a LONG way toward helping that situation out...

[billfrommich]

In the shop I am building in Michigan, I decided not to insulate or even finish (other than paint) the concrete block basement walls, but not on the basis of any temperature/energy concerns. Rather, I was concerned about moisture/mold/mildew problems. It seems like every other home on my street that has "finished" basement walls has developed a problem with mold or mildew. Perhaps this was due to improper wall construction (vapor barrier placement, etc.) - I really have no way of knowing. As far as the basement temperature is concerned in summer and winter, there was a time before we had central air that we used to almost live in the basement during the hottest summer days. And if I remember correctly the temperature crept up into the high 80's even there. In the winter the temperature might drop into the 60's occasionally - you wouldn't be comfortable working in a T shirt but a flannel shirt like Norm wears would be fine. Nowadays, with the central air on in the summer, and given the fact that the cooled household air naturally moves into the basement, it sometimes feels like its colder down there in the summer than in the winter.

[sbs]

Depends on if you are running HVAC in the basement or not.

If yes, then insulate, if no, then not.

My non-insulated, non-HVACed basement stays at a fairly constant temp year round, which tells me that I would not benefit much from insulation.

I just don't understand these Yankee rooms below ground and what they do with them. In Florida, we fill them with water and call them pools. No need to insulate at all.

I am a Southern boy, and hate winter, and am finally getting to move back South soon. But, man, am I going to miss the full unfinished basement.

[jackellis]

Ground temps tend to be pretty stable. I could be wrong about this but once you get below the frost line in cold places, the temp is around 50-60 degrees. That's how an uninsulated basement that's mostly below ground can be mild in winter and cool in summer.

We're installing hydronic heating, so we need insulation and thermal breaks to keep all the energy we put into the slab from warming the ground instead of the floor. I do not want to provide warm soil for the critters that burrow underground in winter!

I *think* the problems with condensation in basements arise because they are not properly insulated on the outside. If the interior of the basement walls that's exposed to inside air can be kept at the same temp as the rest of the house, condensation is not a problem. If the interior surface of the concrete is cool, it'll cause moisture in the air to condense.

All of the inside surfaces of our concrete walls will be furred, with rigid insulation to keep the cool concrete separated from the warm, moist interior air.