Applying KoolCoat In An Attic


In this document I will try and address as many concerns, pitfalls, tips and hints about applying KOOLCOAT on the underside of a roof deck as come to mind. As new ideas come forward or I remember something I left out; I will update this list. Any and all of you are welcome to add your own experiences to this list of do’s and don’ts. Email your ideas to me and I will consider their addition.

Koolcoat Radiant Barrier Paint In The AtticThe most difficult part of applying KOOLCOAT radiant barrier in your attic is getting up there. It is hot and dusty and hard to move around. Sometimes it’s cluttered with stuff someone stored away and forgot. There are sometimes loose wires or un-protected electrical connections. There are things to bump your head on and the always unexpected step through the ceiling drywall. But with some pre-planning and the ever conscience effort to stay safe and sound and get a good job done, you can eventually protect your building from the impact of radiant heat that drives your energy bill up.
Lets get started!

What paint should you use? This is a question I hear regularly. Latex is the logical choice and it doesn’t need to be anything fancy. I recommend looking for miss-tinted paints at the paint stores. Sometimes you can get some really good prices on expensive paints. The colors don’t matter that much, actually you can pour them all together and mix them up.

There are some who would prefer to not hunt around and fool with a bunch of different cans and colors; so for those I would recommend a “Construction-Grade Latex Primer”. Why?  Because it covers bare surfaces very well and provides a thick coat. It also is available in five gallon buckets which make application easier and the cost usually runs around $7 per gallon. Later in this document I will discuss how to determine the amount of paint you will need.

Should you spray or roll?

Rolling a roof deck is hard work. The shingle nails or staples eat rollers pretty fast (figure on using three or four rollers on a 2000 square foot roof deck) and reaching all the spots is difficult without a long handle. Of course a long handle is always getting caught in the roof beams and you have to do everything upside down. Rolling is DOABLE, just be prepared for a two or three session application. Spraying with an air-less sprayer is the preferred way to go. Air-less rentals aren’t cheap and you may have to buy a “tip” or spray orifice that you will keep. To minimize clogs you need to use a .021” tip. The rental unit must have a gun that will accept that large of a tip. Be prepared to give the rental guy all this info so he can set you up with the proper machine. If you want to buy your own or if you already own an air-less, keep the tip size in mind so you get home with all the proper equipment. There are ways you can match a smaller pump with a large gun, and for shooting KOOLCOAT in the attic it works great. Email me and I’ll tell you details about mixing and matching different size parts.

No matter if you have your own or rent a machine, you must remove any filters otherwise the filters will collect all the KOOLCOAT and you will have to do the job over again. Painting with the .021” tip will result in heavy spray volume so plan on being able to move around quickly. To accomplish fast foot work, move any stored stuff so you can get you and your paint hose around without interruption. You may want to have some boards placed in various areas to walk on. I like split sheets of 3/8” plywood. A 2’x8’ plywood plank is just right to scramble around on and they are easy to move from place to place. Whatever you use, it has to go through the man-hole into the attic. Check your clearances before you spend time and money on walking boards.

How much paint will you need?

You need to do some measuring so you know how much paint and KOOLCOAT your project will require. Here’s one easy way to do that. Roughly figure your building’s square footage. If the roof pitch is moderate (not too steep, not too flat) add 15% to the total floor square footage. For example, if your floor area covers 1800 sf, add 15% (1800 x 1.15 = 2070) 2070 square feet is a close approximation of the roof deck area. You can also go up in the attic or on top of the roof and measure from the peak down to the eave, double that number; measure the length of the roof, and then multiply the length times the doubled width. That will result in total square footage of the roof deck.

Since I first put these tips and hints together, my customers and I have discovered that coating the rafters makes a lot of sense. For example if your roof has 2”x6” rafters set 16” apart, the three exposed sides of all the rafters will add about 65% to the surface needing to be coated. Why? Because, if you only coat the decking, heat will continue to conduct down through the roof and into each rafter and then that heat is radiated into the attic. In our above example of the 2070 square feet of roof decking, the rafters will add an additional 1345 square feet! To figure how much paint you need in gallons, divide the total sq. footage by 300. Using the above example, 3415 (2070 + 1345) divided by 300 = 11 gallons per coat. And you need to apply two coats, resulting in a total of 22 gallons.

Many customers report back to me that after two thick coats of KOOLCOAT and paint on deck and rafters (with a well ventilated attic) their attics don’t get any warmer than the outside temperature. So, on average each gallon of paint is going to cover 300 sq. feet of roof deck and rafters. That average is based on the fact that paint mixed with KOOLCOAT may be a little thicker than normal latex and the large tip puts out a lot of paint quickly. The 300 sf/gallon estimate may vary depending how fast you can move and how thick the paint becomes when mixing. It is just an estimate but it is a good number to determine paint volume needs.

Spray KoolCoat In The AtticSo, you now know how much paint you will need for each coat; how many coats will you want to apply? Roof decks get very hot every day of every summer, and this heat dries the moisture out of the wood. Don’t be at all surprised if the first coat disappears into the wood grain. If that first coat has KOOLCOAT mixed in the paint, it will lose about half of its radiant barrier effectiveness. To test your roof deck to see if it is overly dry, spray or roll a small patch of deck with plain paint and watch if it stays on the surface or is absorbed by the dry wood grain. Your test patch should be about the size of a sheet of plywood (4’x8’) so you get a good idea of the wood grain condition. After the paint dries, there may be large spots where it looks like the paint disappeared. This would indicate that you are going to have to apply a “seal coat” of plain paint to seal the dry grain from absorbing your KOOLCOAT. Putting on a seal coat is of course an added expense, but necessary to obtain the best radiant barrier results from KOOLCOAT. Any radiant barrier needs to have an air layer next to it to be effective. No barrier works well sandwiched in wood grain or between layers of construction material.

Thinning your paint for the seal coat application is acceptable. Once the seal coat is on and it is beginning to become tacky, be prepared to start applying the first coat of paint with KOOLCOAT. Actually, the time involved is not long, if your roof deck is 1500 sq. feet or larger, by the time you finish the seal coat the other end where you started will be getting tacky so you can just keep on going without shutting down except to change paint buckets. To obtain the best results from coating your attic, let’s summarize the important points:

Count in all the square footage of decking AND rafters.
Test the wood for dryness and paint absorption.
Once you are satisfied that your paint and KOOLCOAT won’t be lost into the wood grain, apply two thick coats.

Having too much paint and KOOLCOAT is never the problem, you will always find another use for the radiant barrier mix; running out during the middle of the job complicates things. Complex roofs and vaulted false ceilings make measurements and application difficult. If you are having problems arriving at suitable estimate for the amount of paint and KOOLCOAT you will need, please call or email me, as I will be happy to help you.

Now you have determined how much paint your project will require and you have located a source for it, you have ordered the KOOLCOAT and made the decision to either spray or roll it on. I have covered some application techniques in the planning discussion, but here we can look at some optional measures to reduce your energy bill even more. While you are painting the roof deck, you are probably straddling duct work about half the time. Your ducts may have some insulation already covering them, maybe not. In any event I would suggest measuring the temperature coming out of the vent furtherest from the air handler, then apply one coat to the duct (top and sides are usually all you can get to without doing contortions) and then take another temperature reading. One customer reported a five degree drop in air conditioning temperature after painting his ducts. This is a simple task and doesn’t require too much additional paint and makes a tremendous impact on the efficiency of your A/C. If it is apparent that the latex paint may not want to stick well to the duct work, let the first coat get tacky and put on another coat. Up in the attic, without the rigors of weather affecting it, the paint should remain on the duct work for several years, adding extra value to your radiant barrier expenses. If the latex does begin to crack and peel after a time, there’s a good chance you have saved enough energy money to go back up and apply a more suitable paint to the ducts. An elastomeric would be an excellent choice for long life and great results. You’ll need to add KOOLCOAT to any type of paint you apply to the ducts. Some older homes have water piping running through the attic as well as ductwork. KOOLCOATING the water lines can also help in reducing energy costs. When coated with a radiant barrier, warm water stays warmer and cold water stays colder.

While applying the KOOLCOAT in the attic, you need to consider any gable end walls that may face west or south. If these walls are not shaded by trees on the outside they can contribute to keeping the attic hot. Applying a couple of coats of KOOLCOAT to these walls will help reduce heat build-up and add to the beneficial results of the project.

Another item to consider while working in the attic is your insulation. Most forms of insulation trap molecular air within their web of fibers and slow down the rate of heat gain by posing as a “dead air space”. Insulation does work, if it hasn’t settled and if it is covering all of the ceiling area. If you see areas of ceiling that are bare or the insulation is matted down, purchase a roll and add to it. It will only help in the long run.

Outside the realm of using a radiant barrier, but still an important issue in keeping your attic cooler is ventilation. An inspection of the existing vents and their sizing will determine whether this is an area of importance or not for you. To be sized correctly, your building should have more intake area than exhaust. In other words the total area of soffit ventilation should be larger than the total area of ridge ventilation. Powered vents and turbines will work as well as the static vent caps along the ridge. But if you really desire to get full ventilation through your attic, you should consider installing a ridge vent. There are several good ones on the market; the highest rated for air flow is Cor-A-Vent. They have been around longer than anyone else and I personally have used them and their product works wonders.

Getting back to KOOLCOAT application, there are several minor issues that come to mind. Mixing the paint and KOOLCOAT is fairly simple. Whether you are working with five gallon buckets of paint or a bunch of one gallon cans, the most efficient method to get everything mixed is to get at least one (two is better) empty five gallon bucket. In the event you bought a five gallon bucket of paint, mix all the paint and then pour half the paint into the empty bucket. Then add the KOOLCOAT into each half-full bucket. This is accomplished by pinching about half the bag of KOOLCOAT into each half-full bucket. Be sure to wear your dust mask as KOOLCOAT becomes airborne very easily. Stirring KOOLCOAT into the paint will result in some lumps forming; these lumps can be mixed into the paint by working the lumps against the side of the bucket with the stick and breaking them apart. Usually it will take a couple of minutes to thoroughly blend the KOOLCOAT into the paint.

If you are working out of a bunch of one gallon cans, you can follow the same procedure pouring two and (about) a half gallons into the five gallon bucket(s). Once you have the KOOLCOAT mixed into the paint, and if you are working with two five gallon buckets, pour one bucket into the other. You will have some left over, in the second bucket, which can be used a little later once you have used a gallon or so out of the full bucket. Describing this paint/KOOLCOAT mixing procedure takes longer than actually doing it. Because KOOLCOAT is made of tiny hollow glass bubbles, they are very light and mix well into the entire volume of paint. The bubbles don’t sink to the bottom and they don’t seem to float to the top in the time it takes to apply the paint. That said it still makes good sense to occasionally stir the bucket you are working out of. And if you made up several buckets beforehand, you need to stir them up before applying just to make sure all the products are well mixed.

When using the .021” tip, as stated before, a large volume of paint can be applied quickly. Unless you are very careful, there can be and usually is a great deal of over-spray and splatter. If there are items in your attic you don’t want ruined by over-spray and drips it is important to cover these items with a plastic painter’s tarp. I would recommend you get the cheap disposable kind and cover everything you want to protect before starting the painting operation. Don’t worry about any drips and spray that lands on the insulation, it won’t hurt it and may even add some additional protection.

There have been concerns voiced about where to place the paint pump when spraying with an air-less sprayer. Pulling the pump and several buckets of paint into the attic only complicates the operation. It is much easier to add the hose to your equipment and have a helper monitor the pump and change paint buckets when necessary. With enough hose to reach the entire attic without moving the pump and leaving the pump on the floor below the attic access door, you will have less to move around, nothing more than yourself to fall through the ceiling and clean-up is much simpler.

Applying a radiant barrier to your attic is great way to begin to save energy money. With good planning and attention to a few details, you can make an unpleasant job safe, quick and get great results!
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