My Green Kitchen Gets Foil Insulation
For An Additional R-4

This page is about our foil insulation experiment in the kitchen-dinette. Located at the windy north end of the house, this was the room that would most benefit from an additional R-4 of insulation and from having the heat reflected back from all the cooking taking place there. This type of insulation is also an effective vapor barrier, something that was equally important in my quest for energy efficiency.

About Foil Insulation

Foil insulation is actually a triple product: an outer foil layer to reflect the heat; a layer of bubble wrap for extra insulation a layer of vinyl that acts as a vapor barrier Altogether, these layers add an extra R-4 of insulation.

This close-up shows both sides of the type of foil insulation that we used. This combination of foil-bubble-vinyl is only one of several configurations available. It's the one they usually put in the kits for hot water heaters, for instance -- a nice way of using up leftovers (see bottom of page).

Another way that a combination foil insulation-vapor barrier differs from ordinary ones is in the vapor barrier installation technique:

• the product must be stretched very taut;
  
• the strapping is no longer just a support for the drywall: it's an essential part of the strategy because it creates an air space to allow the heat to bounce back towards the room;
  
• the joints must be sealed with aluminum tape in order to preserve the integrity of the reflectivity.

Foil Insulation/Vapor Barrier, Step-by-Step

If you've been following this story, you will have seen the spray foam insulation installment. This photo shows the kitchen-dinette after spraying the wall cavities with spray foam insulation.

With the mess cleared away, we were ready to apply the reflective foil insulation (sometimes called reflective insulation or radiant barrier.)

Due to the mostly northern exposure, it was decided that the kitchen-dinette walls would benefit from this different treatment.

STEP ONE: One final pass with the steel brush to remove spray foam insulation residue before applying the special foil vapor barrier to the walls. It's just not desirable to have lumps and bumps on the studs where the material is going to be stapled.

Follow The Instructions!

That done, and the mess cleared away, we were ready to apply the reflective foil insulation. (NOTE: foil insulation is sometimes called reflective insulation or radiant barrier.)

It's important to read -- and follow! -- the instructions. For instance, they specify that the seams must not overlap. That makes perfect sense, and here they're being trimmed to about halfway across the horizontal stud, where another length is going to abut. But absolute precision in the joint is not essential because the two pieces will be joined with foil tape.

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. (The ceiling has the blue foam insulation.) 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. (Remember, this is not just insulation, it's also our vapor barrier.)

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 it extends beyond the walls at the top, as mentioned above.

Note, also, how the joints are taped with foil tape -- do not be tempted to use other kinds!

The one exception to the above taping rule is the corners. The foil does not resist being bent, as is clear from this photo. The solution I found: apply Tuck Tape first, then foil tape on top of it. Do not be tempted to use duct tape! It will NOT resist, and you won't know it's peeling off because it will be buried within your walls!

Electric boxes get covered with insulation, then they are carefully revealed. Then foil tape is applied all around. Don't wait till you're all done, or you may not remember where they are!

The kitchen walls are basically done. Remembering that this is also a vapor barrier, tape has been carefully applied around electric boxes, windows and pipes, to create a good seal. NOTE: The ceiling and floor overlaps appear very clearly in this picture.

Next, the ceiling receives its standard, clear 6 mil vapor barrier. The red tape is for sealing up all the little staple holes.

Final step: 3/4-inch-thick strapping (or furring strips) is fastened to the studs, and all around doors and windows. That will provide support for the drywall.

Dollar-by-Dollar

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.

Because of the way the job was organized, it's not possible to separate labor costs for this foil insulation project. But it's something you can easily do yourself (you'll need a helper).

Other Uses For Foil Insulation

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, then I wrapped the furnace plenum and all the air ducts with foil insulation and sealed the seams with more foil tape.

I sold that house before I had a chance to take pictures, but this is how it's used on plenums and ducts. 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.

REFLECTIVE INSULATION FOR ATTICS

Most people associate reflective insulation with attics. Used properly, an attic radiant barrier keeps the attic cooler in summer.

The U.S. Department of Energy has an excellent Fact Sheet on the subject of radiant barriers for residential attics.

The Different Types

My online research took me to Ayr Foil website (link will open their documentation page). It 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.

What To Do With The Leftovers

Leftover material can be used for a variety of things, so hang on to whatever you have left.

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 was hoping that the additional cushioning would help absorb some of the noise. I think it does. The foil strip was placed on top of the appliance's own felt insulation, with the foil side facing towards the dishwasher to reflect the heat back.

Other Uses for Foil Insulation

The Resisto Company's website (Resisto manufactures Ayr Foil products) 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

(Please note that I have no association with that company -- this is purely for informational purposes.)

Green Notes

Is Foil Insulation Green? All the components of the foil insulation products may not be as green as we'd like, but there's no real substitute and the energy saved will keep the planet green a bit longer for us and for our children and grandchildren.

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 staying in the kitchen and preventing the thermostat from working, for a while.

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