My Green Kitchen Gets Foil Insulation For An Additional R-4
Step-By-Step Photo Album
Foil insulation (a.k.a. reflective insulation, radiant barrier) is nothing new for me.
I used it in my previous house to insulate the forced-air furnace plenum and ductwork.
The decision was made after I realized that the unfinished basement was unnaturally warm. The ducts were so hot I could barely touch them, and the joints between the different parts, and between the ducts and the furnace, leaked alarmingly.
I did a bit of research, and found that for $25 and a roll of foil tape, I could make sure that the hot air which was costing me $600 a month would be going where it was meant to go.
First, I sealed all the joints with foil tape (they say mastic is better but I couldn't find any), then wrapped the air ducts with foil insulation and sealed the seams with more foil tape.
Here's how it's used on ductwork:
Notice the narrow strips; they're meant to create an air space, which increases the R-value of the insulation.
It worked. As the basement got cooler, my heating bill got smaller.
I also wrapped my hot water heater. For that, I used a kit like this one, that cost about $25.
Note that for this application, the foil is inside, facing the tank.
That was for a previous house. For the green home that is the object of this site, I made my water heater jacket with used leftover foil insulation. See the step-by-step description on this page.
Foil Insulation Is Also A Vapor Barrier
But I didn't know that foil insulation was also a vapor barrier. I found that out by doing some more research this year.
Since I needed to apply a vapor barrier everywhere, I felt that this product merited serious consideration for its double potential.
The Ayr Foil Guide (PDF file) (Ayr Foil is the name of the product, which is manufactured by Resisto) was the one with the most complete information, and that happened to be the brand that I had used the last time, so I went with it.
The Guide told me that the product I needed was the one known as "A1V", commonly described as foil-bubble-poly, that is to say:
one layer of foil
Polyethylene backing
one layer of Polyethylene bubble
one layer of white Polyethylene
(The product I had used previously was "A2A", or Foil/Polyethylene backing/Polyethylene bubble/Polyethylene/Polyethylene bubble/Polyethylene backing/Foil.)
What I appreciated about that brochure (by the way, I'm not getting paid for this propaganda!) was how well it explained how it should be installed, and why.
The reason that foil insulation is more effective than a standard vapor barrier is that the foil reflects the heat back ito the room. But to achieve this effect, it must be installed properly.
That means creating an air space between it and the wall finish, with 3/4-inch strapping every 16 inches. (3/4-inch being the minimum.)
The space is needed to help the heat bounce back, so to speak.
It was important to know this, because my builder had no experience with this product.
Good Customer Support
I phoned the company to confirm my choice and get answers to my questions, and I got excellent service from the customer service personnel.
In the end, I chose the above product (the one with only one foil layer), because with foil on both sides, you have to double-strap your walls: once before installing the insulation and once after. I just couldn't justify all that extra expense.
Obviously, I couldn't afford to cover all the house with this product, but I was anxious to try it somewhere.
I determined that the room that would most benefit from the additional R-4 of insulation and from having the heat reflected back would be the kitchen-dinette, given that it was located at the windy north end of the house, and the fact that I do a lot of cooking and would like to keep the heat thus generated inside the house, thank you very much.
(Keeping the heat out is not a problem in this Maritime climate. Summers days are not hot and nights are always cool.)
Foil Insulation/Vapor Barrier, Step-by-Step
If you've been following this story, you will have seen the foam insulation instalment.
This is the way the walls looked -- minus the débris -- when we started applying the foil insulation.
The instructions specify that the seams of the foil insulation must not overlap; here they're being trimmed to about halfway across the horizontal stud, where another length is going to abutt.
Another very important point is that the material be stretched as tautly as possible.
This is to facilitate the reflectivity: think of it as a drum or a trampoline!
Therefore, two people were required for the installation: one to stretch and one to staple.
Note how the edge extends beyond the angle where it meets the ceiling.
This is so that it may be sealed to the ceiling vapor barrier.
What's true of the ceiling is true of the floor, since it's important to avoid any sort of gap where cold air can enter or warm air leak out.
Foil insulation usually comes in 16", 24" and 48" widths.
We chose the 48-inch, which spanned three studs perfectly, cutting down on labor.
Note how the joints are taped with foil tape -- do not be tempted to use other kinds!
The one exception to the above rule is the corners.
The foil does not resist being bent.
The solution: Tuck Tape first, foil tape on top of it.
Electric boxes get covered with insulation, then they are carefully revealed.
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The kitchen walls are basically done.
Remembering that this is also a vapor barrier, tape has been carefully applied around electric boxes, windows & pipes, to create a good seal.
Next, the ceiling receives its standard, clear 6 mil vapor barrier.
There is a lot of red tape because the staples all have to be sealed; otherwise, we'd have hundreds of tiny holes, and a vapor barrier with holes is not acceptable.
Final step: 3/4-inch strapping is applied, every 16 inches or so.
It will provide support for the drywall.
Note that here, too, the staples have been sealed with tape.
Cost of Materials
The cost of the 400 square feet roll (100 feet long by 4 feet wide) was $108, plus three rolls of foil tape and plus labor of course. Labor would have been required no matter what kind of vapor barrier I used but my builder said that this was quite a bit more labor intensive.
I will never know how much energy or money this particular area is saving me since this was a whole house insulation project. But I know I will feel good, when it's minus 30 outside and I'm baking bread, that some of the oven's heat is preventing the thermostat from working, for a while.
What To Do With The Leftovers
Leftover foil insulation can be used for a variety of things, so hang on to whatever you have left.
FOR THE HOT WATER HEATER: I had enough material left to insulate my hot water heater and all my hot water pipes.
FOR WATER PIPES: To insulate water pipes, you cut the material into long strips, which you wind around the pipes. Fasten with foil tape. It's simple, and a good way to use up all the trimmings too.
FOR THE DISHWASHER: When I installed the dishwasher, I found the insulation that was supplied much too flimsy.
I used the felt insulation that was supplied as a pattern for the foil insulation.
The foil insulation was placed on top of the felt insulation, with the foil side facing towards the dishwasher to reflect the heat back.
Dishwashers tend to be noisy, so I was hoping that the additional cushioning would help absorb some of the sound.
Reflective Insulation for Attics
Most people associate reflective insulation with attics. Used properly, an attic radiant barrier keeps the attic cooler in summer.
The Resisto Company's brochure describes many different uses for its radiant barrier insulation:
Crawl space
Walls and ceilings
Inside retrofit
Concrete block wall (foundation walls)
Metal building insulation
Post frame and pole buildings
Water pipes and air ducts
Water heater tank
Underneath a concrete slab
Radiant heating under a wood floor
Garage door
Sheds and huts
Cathedral ceilings
For additional information, you might want to consult the Reflective Insulation Manufacturers' Association (RIMA) Handbook.
Is Foil Insulation Green?
Foil insulation may not be the greenest material, but it's the only one of its kind and the energy saved will keep the planet green a bit longer for us and for our children and grandchildren.
