Before even discussing Radiant Barrier, it is important to understand all the issues with cold climate insulating and retrofitting an old house or modern home with insulation. There is a plethora of issues and technical problems that must be addressed and understood which, brings into the discussion, talk to the pros, the real ones who have been in business for decades. Research and learn, one can never do enough of that for a project.
An interesting bit of history is that buildings used to be built for their location. Homes in the North had fireplaces in the center of the house maximizing heat gained. In the South, they were moved to the exterior wall of the homes or, even outside. From the 50’s to the 70’s, technology (HVAC) was thought to solve and used to solve all our problems regardless of location. This produced housing types that were identical throughout the country, ignoring climate or environment. Homes today are more comfortable however, we cannot keep up with the increased energy demands and as there are more and more gadgets with appliances even when they are Energy Star efficient, our energy and utility demands have increased.
The best solution to this would be to combine the latest and best up-to-date technology with the design concepts of earlier homes and produce truly efficient structures designed for one’s climate and location.
The BIG key to insulating is, “location, location, location!”
More is not always the best way to improve or make a home efficient. Due to a higher heat load on the roof vs walls, adding more insulation to the wall does not always improve the outcome.
R-13 absorbs 93% of conductive heat, upgrading to R-40 will reduce the heat flow by only an additional 5%. Wow. However, adding insulation to the right locations can and will improve efficiency.
Cold climate insulation requires high levels of thermal insulation in the five main areas of a home. These are the attic, walls, floors, crawlspace, and basement. In areas where it is extremely cold, high levels of insulation make a big difference. The later two are the most overlooked areas needing insulation in cold climates and in severely cold climates, the slab needs insulating.
For an unconditioned basement, the ceiling needs to be insulated keeping heat upstairs in the living space from passing through. This is the same for an unheated garage with living space above. A conditioned basement is heated intentionally or heated just due to the presence and functioning of the water heater or heating system. The basement walls in a conditioned basement need insulating and any frame walls in the basement. The ceiling however does not. Slabs at grade foundation should be insulated at the edges where the slab is exposed to cold air. This is a small surface area but poses a significant heat loss area which, increase heating costs and makes interior floors colder in the winter.
How can Radiant Barrier play a role in cold climate insulation? There are numerous ways and yet most of the information available is word of mouth, articles all badmouthing radiant barrier as totally inappropriate for use in colder climates citing zero possible use and results. This is incorrect.
What IS true, is there is not much radiant heat loss in a cold climate home BUT, radiant barrier helps the attic insulation work efficiently up to or very close to its R-value making it more effective and this is the same for basement and crawl space insulating. The barrier is put closest to the heat source to prevent the heat from leaving the heated space.
A typical ventilated attic assembly is roof, attic space, attic insulation, sheet rock. Air enters the soffits, exits the exhaust vents removing moisture laden air and keeps the roof cold preventing ice dampening. The only thing between the warm living space and the cold outside air in the attic, is the sheetrock and a layer of thermal insulation over that.
This presents a substantial failure in creating an energy efficient home because we are blowing air into the attic insulation layer with out a top barrier. To fix this, the insulation needs a “jacket” per se. Without the barrier layer, it is akin to a jacket without the outer wind protection layer on a cold and windy day.
Insulation does absolutely zero to stop airflow and since most of that insulation is fiberglass (think about air filters being made of fiberglass), allowing maximum unrestricted air flow. The whole idea behind R-value is based on trapped or dead, nonmoving air. For example, inside a wall or a jacket or down comforter, there is very little air movement. Add in wind and no barrier, the thermal insulation becomes worthless. To solve this problem, radiant barrier enters the stage. It should be placed directly over the attic insulation minimizing air movement or what is called convective looping, inside the insulation and reduces radiant heat loss although very little, but brings the R-value of the thermal insulation up to efficiency rating. The radiant barrier will reflect the absorbed heat from the thermal layer back down to the living area keeping the air on one side warm and the attic side, cool.
Convective looping is when the cold dense air “falls” through the insulation displacing the trapped warm air in the thermal layer close to the sheetrock. It is literally the pumping of air through the attic ceiling insulation.
Radiant barrier for this type of application must be PERFORATED to prevent moisture from collecting inside the attic insulation under the foil and turning to water or ice. This adds one more task to the application, that of sealing all holes from lights, can lights, fixtures, whatever there may be in the ceiling sheetrock and edges tight as a drum otherwise, too much moist warm air will enter into the insulation and condense unable to dry out.
Again, important note, the radiant barrier must have the proper air space so if installed over insulation, the attic air space will be sufficient. In very cold climates the radiant barrier needs to be closest to the heat source. By creating a dead air space behind sheetrock, the heat will convert to radiant heat to jump across the airspace. Once it does, this heat meets the foil layer and is reflected back down to the interior. By preventing heat from escaping, the radiant barrier allows the outside layer of traditional insulation to be more effective.
To prevent condensation, radiant barrier for this application must have a high permeability rating and perforated. In extremely cold climates, a vapor retarder should be used between the sheetrock and thermal insulation, proper attic ventilation and control high living space humidity levels. Dehumidifiers in artic living can be helpful.
One last note, air sealing is fundamental: doors, windows, chimneys, electrical and plumbing penetrations, and baseboards.