Tag Archives: fiberglass batts

Attic Insulation Types

Attic insulation has been a recent popular topic of discussion – so rather than reinventing the wheel, I’m sharing a relevant article written by Structure Tech Home Inspector Reuben Saltzman.
Originally published by the following source: Minneapolis Star Tribune — February 6, 2018
The following article by Reuben Saltzman was produced and published by the source above, who is solely responsible for its content. Hansen Pole Buildings is publishing this story to raise awareness of information publicly available online and does not verify the accuracy of the author’s claims. As a consequence, Hansen Pole Buildings cannot vouch for the validity of any facts, claims or opinions made in the article.

What’s the best attic insulation? That depends on your definition of “best”. What’s going to perform the best is definitely not the most cost-effective way to insulate an attic. But surely, you already knew that.
And I didn’t call you Shirley.
First, let’s discuss the most common types of insulation available for attics; spray foam, loose-fill fiberglass, cellulose, and fiberglass batts. Those aren’t the only types available, but they make up the vast majority of what’s used in Minnesota attics. For the listed R-values below, this refers to the material’s ability to resist the transfer of heat and is all per-inch. The higher the number, the better. The minimum R-value for a new Minnesota attic is R-49.

Fiberglass batts
Unfortunately, the easiest way to add insulation to just about any place in your home is to install fiberglass batts.  Fiberglass batts are typically the worst insulation for any job, but they’re easy to pick up in the store and easy to roll out, so people use them. The image below shows an atrocious installation at a two-year-old home in an upscale neighborhood of an inner-ring suburb of the Twin Cities. Yep, this passed the city inspection.

I won’t even discuss R-value because fiberglass batts have no place in an attic. Just don’t go there.

Cellulose
Cellulose is made from recycled, ground-up paper with boric acid added for insect control and fire resistance.  If you choose to install cellulose yourself, you can buy the insulation in bags from your local home improvement store. If you buy enough, they’ll probably let you use an insulation blower for free. Don’t try to buy a single bag and spread it out by hand for spot-insulation; it’s way too densely packed (ask me how I know). The DIY cellulose insulation method is very dusty, but it’ll get the job done.  If you hire a pro, they’ll use wet-spray cellulose, which adds a small amount of water to the cellulose to help control the dust and to slightly increase the insulation value per inch.

Cellulose has an R-value of approximately 3.5 per inch. The part that I love about cellulose is its ability to control air movement. While it doesn’t actually create an air barrier, it’s dense enough to stop most air movement to help control frost in attics. Not completely, of course, but it does a pretty good job. The same cannot be said for fiberglass.
If you check with the Cellulose Insulation Manufacturers Association, they’ll assure you that cellulose is definitely your best choice for insulation.

Loose-fill fiberglass

This seems to be all that’s ever used in new-construction homes and has an R-value of approximately 2.5 per inch. Like cellulose, you need a big machine to blow it in. You can’t simply buy it in bags and spread it around yourself. My biggest complaint with fiberglass is that it’s itchy and it’s a lung irritant. I’ve found that older fiberglass is way worse on your skin and lungs than the newer stuff, however. I have no scientific evidence to back this up, but I don’t need any. I’m completely sure of this based on personal experience.

Side note: I wouldn’t dream of doing any type of insulation work without wearing a respirator. Heck, I won’t even enter an attic without one.

There was a widely publicized study conducted by Oak Ridge Laboratories in 1991 that said that loose fill fiberglass insulation lost a lot of its insulation value once temperatures dropped below 20 degrees, making loose fill fiberglass an inferior product when compared to cellulose.  I contacted Andre Omer Desjarlais at Oak Ridge Laboratories about this issue, and he said: “This was true 20 years ago but all fiberglass manufacturers have changed their products appreciably since then and this is simply no longer an issue.”  I also contacted several insulation manufacturers about this, and they said the same thing and sent me some great information, which I posted on my website many years ago; click any of these links to read the documents from Certainteed, Johns Manville, or Owens Corning.  Loose fill fiberglass insulation will still experience convection, but not nearly as much as old fiberglass used to.
If you check with the North American Insulation Manufacturers Association, they’ll assure you that fiberglass or mineral wool is definitely your best choice for insulation.

Spray foam
From a performance standpoint, the best type of insulation is spray foam. There are two types; closed-cell and open-cell, aka 2-lb and ½-lb, respectively. They have insulation values of approximately R-6.5 and R-3.6 per inch, respectively. When installed properly, both types of insulation will fill all of the nooks and crannies and make for a perfect air barrier. When air can’t move through it, you have zero heat transfer through convection. Oh, and by the way, Icynene® is a brand name of open cell foam.

With closed-cell foam, you also get a moisture barrier at over 2″ thick. Because of this and the higher insulating value per inch, most foam insulation used in Minnesota is closed-cell. To tell the difference between the two, try poking it with your finger. You can easily poke a hole in open cell foam, but not closed-cell foam. That stuff is way too hard.

 

The big downside to either type of spray foam insulation is the cost. It’s expensive stuff, and it shouldn’t be installed by the DIYer. Of course, that’s not to say it can’t be done, it just shouldn’t be done. Professionals already have a hard enough time getting it right. Check out this article for more on that topic: Avoiding Problems With Spray Foam. The image below shows a botched spray foam installation at the rim joist of a new-construction home that I inspected.

A concern with spray foam insulation is the off-gassing of toxic poisons. I’m no expert on that matter, so I won’t discuss. Just be aware that it’s a concern, and do your own research. After conducting my own research, I concluded that I was comfortable putting it in my own home.

How to Properly Insulate between Roof Purlins

How to Properly Insulate Between Roof Purlins

Efficient climate control is becoming the buzz term for post frame construction. A challenge occurs when clients look to insulate between their roof purlins.

Reader JOHN in COVINGTON writes:

“I am building an all wood pole building. The purlins are 2x8s. I want to insulate the walls and up at the purlins to keep as much usable space as possible with an insulated building. How do I insulate and properly vent between the insulation and the underside of the plywood roof underlayment. If I use R19 it is 6 inches so there would be 2 inches of space between the insulation and the wood. Do I use something like a house bird block at each end of the building for each purlin space?”

Mike the Pole Barn Guru Writes:

The best solution lies in creating an unvented roof

It is quite possible to design an unvented insulated roof assembly which performs well, as long as you get the details right. In recent years, most building codes have begun to allow the construction of unvented insulated sloped roof assemblies. Many such roofs have failed over the years, however, so don’t get creative. Follow the rules.

For sake of brevity, I will limit this discussion to only as it pertains to post frame buildings with widely spaced trusses and purlins on edge.

First of all, you can’t use air-permeable insulation (for example, fiberglass batts, mineral wool batts, dense-packed cellulose, or blown-in fiberglass) to insulate an unvented roof assembly unless the roof assembly also includes a layer of air-impermeable insulation (spray polyurethane foam) directly below the roof steel or sheathing.

The 2009 IRC (International Residential Code) defines air-impermeable insulation as “an insulation having an air permeance equal to or less than 0.02 L/s-m² at 75 Pa pressure differential tested according to ASTM E 2178 or E 283.” Although spray foam insulation and rigid foam insulation meet this standard, fiberglass batts and dense-packed cellulose do not.

If you want to use just one type of insulation in unvented bays, you are limited to spray polyurethane foam. Another possibility, of course, is to build your roof with structural insulated panels (SIPs), which in most cases is cost prohibitive.

The code restrictions on the use of air-permeable insulation between purlins were developed to prevent the purlins or roof sheathing from rotting. When fiberglass batts are installed in unvented bays, the batts allow moist indoor air to reach the cold steel roofing or sheathing. That leads to condensation or moisture accumulation, followed eventually by rot. Since spray foam prevents air movement, it almost eliminates this problem.

It’s important to note, however, recent research suggests closed-cell spray foam is much less risky than open-cell spray foam in this location.

To summarize, there are really two practical ways to build an unvented roof assembly:

Install closed-cell spray foam against the underside of the steel roofing or roof sheathing, and no other type of insulation. Be sure the thickness of the spray foam is adequate to meet minimum code requirements. Remember open-cell spray foam is risky in all climate zones, and if open-cell spray foam is installed in this location in a cold climate, the underside of the cured foam must be covered with gypsum drywall which has been painted with vapor-retarder paint. Vapor-retarder paint is ineffective if it is sprayed directly on the cured foam.

Install a layer of closed-cell spray foam against the underside of the steel roofing or roof sheathing, and fill the rest of the purlin cavity with an air-permeable insulation. This type of assembly is designed to dry to the interior, so the assembly should never include an interior polyethylene vapor barrier.


 

Fiberglass insulation in pole buildings

The best time to insulate your new pole building…is at the time of construction. There are many building features which are more easily done at time of construction, but sometimes the old pocketbook only stretches so far.

At the very least, if you can prepare your building for future “additions” of features such as additional doors, windows, and insulation, you will be time and money ahead.  In the building planning stage, one of the “lists” you might want to make in order to make the best decisions in designing and ordering your new pole barn, is “what are all the possible uses of my building going to be?”  I’m talking not just in the next few months, but way down the road, like even five or more years from now.

Many times what starts out as a simple accessory building, becomes so much more. With the recent challenges for folks selling and purchasing properties and homes, I’ve seen a huge surge in clients building their garage/accessory building on a new building site before they even think about building their new home.  Whether due to waiting to have the former house and real estate sold, or just not enough cash flow to make it all happen at once, more clients have been opting to insulate their pole buildings and live in them while the rest of their plans come to light.

With this in mind, designing for insulation is important.  On my most recent personal building, for example, knowing I wanted to be comfortable in shirtsleeves in -40 degree weather, (and not pay to heat the outside world), I chose to put in deeper outside walls of my building than were necessary by code, to accept a thicker insulation I also put in fiberglass insulation within the interior walls, as part of the building was “cold storage” separating the warmer areas by interior walls.  So let’s talk about fiberglass insulation.

Fiberglass itself is not some “magic” insulator, it is the dead air trapped in the fiberglass which is doing the work. Smash the air out, and you lose R value.

This is not to say fiberglass insulation, is still not one of the most affordable and best insulation choices.  Sometimes it just comes down to two questions: 1. Will it do what I want it to?  And 2. Will the cost of the product and installation be a good investment over time?

With proper advance structural planning, roof purlins and wall girts can be spaced at 24 inches on center. This will facilitate the later installation of batt insulation. Properly installed, this method can be effective for maintaining a controlled climate within the building. Installation of kraft (paper faced) fiberglass insulation is relatively quick, as it is manufactured with staple tabs along the sides of the rolls for easy application. Many professional installers prefer to use unfaced insulation and add a clear vinyl visqueen vapor barrier to the inside of the fiberglass/framing assembly. In either case, with a tight seal it is clean, neat and contributes to mold prevention and pest control.

I would be remiss if I didn’t advise you to be safety conscious during installation.  Put on protective gloves, a dust mask and goggles when working with insulation. Insulation is made of tiny fiberglass shards, which can cause serious irritation of the skin, eyes, nose and throat if you don’t take proper precautions.

Overall fiberglass insulation batts remain an easy to install option and affordable choice for condensation, climate, mold and pest control.