Insulate Basement Ceiling

Insulate Basement Ceiling

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
insulate basement ceiling 1

Insulate Basement Ceiling

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
insulate basement ceiling 2

Insulate Basement Ceiling

Greg, Thanks for writing. Yeah, Wisconsin can get cold. My aunt has a farm on the St. Croix river that they’ve converted to livable space over the years but man it was cold in the winter. You could insulate the ceiling. I’m not saying it doesn’t work at all just that attacking the basement walls is far superior. You can spray foam just make sure you entirely encapsulate the basement ceiling joists. Sometimes the applications are much heavier in the bays than on the joists when it really should be evenly applied. You might consider an approach like I mentioned a few posts up, using batts then adding taped foam board. This could be removed later if you decided to insulate the basement walls where a foam application is pretty permanent. Also, if insulating the ceiling leaves your pipes outside the thermal enveloped, they need to be well insulated otherwise you will create a problem. Erik Reply
insulate basement ceiling 3

Insulate Basement Ceiling

First, you’ll have to maneuver batts of insulation around the clutter of wires, pipes, and cross bracing in a typical basement ceiling. Hold the batts in place by stapling their paper-faced vapor retarders to the lower edges of the joists. Once the ceiling is buttoned up, insulate the rim joist—the floor framing around the perimeter of the house directly above the foundation wall. And now that your basement is going to be cold in the winter, you’ll also need to insulate any ductwork and hot-water pipes that are below the ceiling, weatherstrip the basement door, and wrap a thick layer of fiberglass around the water-heater tank. In other words, you’re in for a lot of work.
insulate basement ceiling 4

Insulate Basement Ceiling

Examples of where to insulate. 1. In unfinished attic spaces, insulate between and over the floor joists to seal off living spaces below. If the air distribution is in the attic space, then consider insulating the rafters to move the distribution into the conditioned space. (1A) attic access door 2. In finished attic rooms with or without dormer, insulate (2A) between the studs of “knee” walls, (2B) between the studs and rafters of exterior walls and roof, (2C) and ceilings with cold spaces above. (2D) Extend insulation into joist space to reduce air flows. 3. All exterior walls, including (3A) walls between living spaces and unheated garages, shed roofs, or storage areas; (3B) foundation walls above ground level; (3C) foundation walls in heated basements, full wall either interior or exterior. 4. Floors above cold spaces, such as vented crawl spaces and unheated garages. Also insulate (4A) any portion of the floor in a room that is cantilevered beyond the exterior wall below; (4B) slab floors built directly on the ground; (4C) as an alternative to floor insulation, foundation walls of unvented crawl spaces. (4D) Extend insulation into joist space to reduce air flows. 5. Band joists. 6. Replacement or storm windows and caulk and seal around all windows and doors. Source: Oak Ridge National Laboratory
insulate basement ceiling 5

Insulate Basement Ceiling

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?
insulate basement ceiling 6

Insulate Basement Ceiling

Dear Erik, I read your article with great interest. My question is , one side of my basement is about 50% out of the ground(the way it was landscaped to take advantage of the view), and should I insulate the ceiling near the wall that is out of the ground or should I make sure to insulate the wall on this side. I have like a French double door to get stuff in and out of the basement on this wall as well. I was thinking about some sort of air lock apparatus for this area. Any ideas would be greatly appreciated. Sincerely, William A Miller Reply
insulate basement ceiling 7

Joann, Thanks for writing. Sounds like a textbook case for insulating the basement walls. The question I always pose to contractors and homeowners who want to insulate the basement ceiling is: Did you insulate the interior walls of the stairwell? Because unless that stairwell is air tight and insulated, you have a 80 square foot hole in your insulation. Erik Reply
insulate basement ceiling 8

We live in northern wisconsin and our basement is not heated, temps reach freezing. To improve heat retention in living area, would it be a good idea to insulate basement ceiling with spray foam. would hope to insulate walls later but they have many, many leaks and it seems overwhelming to me now. Reply

Leave a Reply