Basement Ceiling Insulation
Erik, Great information. I’ve also read the “How to insulate basement walls” article. We are about to refinish our entire basement. It’s a split-foyer home on a slite hill, so part every basement wall is below grade. Walls are formed concrete. Builder installed fiberglass insulation to walls with shiny barrier surface facing basement interior. Every wall in basement will be framed and dry-walled. We are also adding a suspended ceiling. We installed an internal french drain system 2 years ago with two sump pits/pumps as well as doing things like ensuring gutter water is channeled from house. We also have propane back-up generator to power sumps in extended poweroutage. I have painted part of the basement walls with two coats of masonry water-proofing paint. My plan is now to insulate the walls vice the ceiling. But I have a two-fold question for you regarding the wall insulation: should I finish adding water-proofing paint to rest of wall, and if so, do I need to add the DOW extruded insulation layer between the wall and framing? My thinking is that the water-proofing paint would serve the same purpose as the DOW insulation. Thanks, Gary Reply
Basement Ceiling Insulation
The quintessential multi-faceted question- Answer: yes, no, and maybe. I’m guessing this isn’t new construction. Currently, IRC (International Residential Code) the residential arm of ICC (International Code Council) requires homes that are built on a basement and the basement is unconditioned, the ceiling be insulated. It is explained as the “building envelope”. A cocoon as it were- of the living area. The science behind it is transference. As you heat the “living area”, that space wants to cool to the temp of the cooler basement temp (an equaling as it were). However, if you reverse the thought process- Cooling the “living space” (hot air rises- cool air falls) then the insulation should help maintain the temp without the transference of temperature. Before this thinking came about obviously there was no insulation. Or if the basement was walk-out, whatever portion of framed wall would be insulated. Concrete foundations (poured wall) are poor insulators (about R-1 for an 8-10″ thick wall) onto themselves. And this is the only true consistent since soil types vary so much. But, the earth surrounding the basement does have an insulating value. Some convening authorities only requires the perimeter to be insulated- the joist band and 4-5′ of the ceiling were required. A very good argument has come about in the insulating a basement debate. ICF’s (insulated concrete forms) are stay in place forms- they are not removed when the concrete is formed. They create a foam sheathing on the outside and inside of the foundation wall. Giving a much enhanced R-value to the foundation wall. The negative has been damage to the exterior when backfilling (and some waterproofing companies will not treat ICF’s because of the damage potential and/or incompatibility of materials) and it provides a dark moist travel highway for termites. So, the best alternative is to install foam board to the interior side of the foundation (1″ minimum) with all seamed sealed with seal tape. From the financial aspect- insulating a basement ceiling could be worthwhile depending on current/area fuel costs. But generally, it would be a long time return investment. The important thing to remember here is this- unconditioned space. So, depending on the sq/ft would it be worthwhile to “condition” the space even though it’s not finished?
Basement Ceiling Insulation
Eric, I think you have the right idea but you seem to be misguided in your knowledge of thermodynamics: “follow the laws of thermodynamics. Heat will flow from the main section into the basement and out into the surrounding air and ground.” Heat isn’t going to flow to the basement. If that were truly how thermodynamics worked a hot air balloon would never get off the ground. Hot air rises, cold air doesn’t. That’s why the most important part of a house to insulate is the attic, it caps off the heat loss, just like a hot air balloon. You can think of your house as a hot air balloon. And that’s why you don’t insulate the basement ceiling. Hot air in the basement will rise, the cold air will stay in the basement. You’re not accomplishing anything by holding down cold air…that’s not going anywhere anyway. If you assume hot air goes down to the basement, it would make sense to insulate the ceiling, but that’s not the case. Insulate the walls of the basement to keep the basement warm as cold walls will cool the heated basement. Also, if you open a door or air seeps out the top of the house, that hot air will escape to be replaced by the cold air from the basement. Reply
In general, but especially during the summer months, moisture can seep through your walls and get absorbed by your insulation. This leads to the formation of condensation that can eventually cause mold, rot and reduced insulating performance. For this reason, fiberglass insulation usually needs to be avoided when insulating your basement. Closed-cell foam tends to be the insulation of choice, but you also don’t necessarily want to pick a contractor who knows just enough about basement insulation to go all out, causing you to spend more money than you have to. Finding a contractor who has a number of years of experience installing basement insulation in your specific region/climate can make all the difference.
A properly insulated basement can save you money on heating and provide a dry, comfortable living space. In most cases, a basement with insulation installed on its exterior walls should be considered a conditioned space. Even in a house with an unconditioned basement, the basement is more connected to other living spaces than to the outside, which makes basement wall insulation preferable to ceiling insulation.
Everything is great until winter starts. You notice your heating bill hasn’t improved that much. You’ve never had standing water but recently the basement has smelled mustier. Mold has started cropping up on underside of the floor joists. Ten years of maintenance-free plumbing ends this winter when the pipes freeze twice. Finally after installing a gorgeous new natural gas sealed combustion boiler (with on demand hot water!), the nightmare scenario occurs: you wander into the basement to find 4 inches of water from the burst pipe. So what happened? Insulation slows the transfer of heat. Prior to insulating the basement ceiling, warmth is radiating from the heated first floor into the cooler basement space. Adding insulation cuts off this heat transfer. Compounding that is the sealed combustion installation. The older giant cast iron boiler was a huge thermal mass radiating heat into the basement space. The two changes would lower the basement temperature by several degrees.
Given the problems with fiberglass insulation in the basement, Dr. Energy Saver developed an alternative solution using rigid foam insulation. Unlike fiberglass batts, rigid foam insulation won’t absorb moisture, compress, lose R-value or fall out of place. It has ideal characteristics for use in the basement, which is why we recommend three innovative basement insulation products.
Hi Erik, Great articles you have written. We live in Mass., house is 27 yrs old. The entire basement is underground, no exterior egress and two at grade windows with little ventilation. Moisture and a musty smell have always been noticeable. There is fiberglass (pink) insulation in the ceiling, paper side up. In some areas, this insulation is dark. Should the basement ceiling insulation be removed and the concrete foundation walls be insulated instead? The walls were Drylock’ed a few years back and this greatly reduced the summertime humidity. Now we just run fans and not the dehumidifier. In winter, the basement is just cold. Thank you for all of your information.
Hi Erik, Great articles you have written. We live in Mass., house is 27 yrs old. The entire basement is underground, no exterior egress and two at grade windows with little ventilation. Moisture and a musty smell have always been noticeable. There is fiberglass (pink) insulation in the ceiling, paper side up. In some areas, this insulation is dark. Should the basement ceiling insulation be removed and the concrete foundation walls be insulated instead? The walls were Drylock’ed a few years back and this greatly reduced the summertime humidity. Now we just run fans and not the dehumidifier. In winter, the basement is just cold. Thank you for all of your information. Reply
Basement ceiling insulation is one of the simplest additions you can make to increase energy efficiency and make the temperature more comfortable. But, unlike insulation in walls, a basement ceiling is often lined with pipes, wires and interconnected beams that will make insulating a ceiling a bit trickier. Insulation will have to be weaved around and behind the various pipes and wires, and then stapled into place.
Basements are notorious for being cold, dank areas that homeowners avoid as much as they possibly can. The heat from your home can quickly escape through the basement and its immediate connection to the ground. This connection leads not only to the cold air associated with the basement but a higher moisture content that makes the basement unpleasant to be in. The basement also conducts heat from the main floor of your home, leaving that floor colder and raising energy costs. Basement insulation is often the answer many homeowners come to, but too many homeowners take short cuts causing them to re-install different insulation after no more than a year or two.