Tag Archives: blown in fiberglass insulation

Blown-In Fiberglass Attic Insulation

Blown-In Fiberglass Attic Insulation

In Climate Zones 3 and higher blown-in fiberglass attic insulation is extremely popular due to lower investment cost and high performance.

Looking for a best solution for your barndominium or post frame attic? It is inevitable an insulation contractor will warn you away from blown-in fiberglass due to a dated study proving fiberglass insulation loses up to half its R-value due to internal convection. It is important to understand this study’s results.

Titled Thermal Performance of Fiberglass and Cellulose Attic Insulations, this paper describes research done by Kenneth E. Wilkes and Phillip W Childs at Oak Ridge National Laboratory 30 years ago.

Wilkes and Childs set up an attic test module simulating temperature differences across an insulated attic floor.  Basically they put a whole roof and attic assembly into big chamber and measured R-values of three insulation types:

  • Loose-fill fiberglass
  • Fiberglass batts
  • Loose-fill cellulose


They kept temperature below the ceiling drywall at 70° F and varied the exterior temperature from 45° F down to -18° F.   Here’s what they found:

  • Fiberglass batts and loose-fill cellulose performed as expected at a whole range of temperature differences. 
  • Loose-fill fiberglass showed a significant reduction in R-value as the attic got colder and the temperature difference got larger. 

Loose-fill fiberglass lost 35% to 50% of its resistance to heat flow at temperature differences of 70° F to 76° F.  This loss of R-value started at a temperature difference of about 32° F.  With temperature below ceiling drywall held at 70° F, R-value started dropping when attic temperature was reduced to 38° F and had lost 35-50% when attic temperature got to 0° F and below.

In looking at this data, researchers saw a pattern leading them to suspect convection within insulation as the culprit.  They did some calculations and further experimentation and concluded this was indeed what was occurring.  Further experimentation they did was to put a covering layer over the loose-fill fiberglass top.  They tried both a polyethylene film and fiberglass blanket combination and (2) R-19 fiberglass batts.  Both eliminated convection and reduction in R-value.

If our story ended here, the lesson learned would be to avoid loose-fill fiberglass for attic insulation or use it with a covering layer.  But there is a Paul Harvey….

If you read this paper and think about what they did and what they found, a couple questions might occur to you.

Why would loose-fill fiberglass and fiberglass batts behave differently in an attic?  They’re made with the same material and were of similar density.

Is fiberglass made and installed now the same as it was back 30 years ago when they did this research?

This Oak Ridge paper doesn’t say what brand of loose-fill fiberglass insulation they used, but at least two fiberglass insulation manufacturers have written technical bulletins about their product and shown data about measured R-values under conditions similar to those studied. 

Density of fibrous insulation materials is certainly an important factor.  But, fiberglass batts and loose-fill insulation used were of similar density.  Batts were 0.46 to 0.48 pounds per cubic foot (pcf) and loose-fill ranged from 0.40 to 0.56 pcf.  So density doesn’t explain any discrepancy.

What does explain it, according to Owens Corning and Johns Manville, is chunk size.  Fiberglass batt or blanket insulation is one large chunk with a lot of glass fibers bonded together.  Thirty years ago, Owens Corning loose-fill fiberglass was made by taking their fiberglass blanket insulation and cutting it into little cubes. Johns Manville doesn’t say how they were making loose-fill fiberglass then, but they do say they used these research results to establish design specifications for all of Johns Manville’s loose-fill fiberglass attic insulations to improve winter thermal performance.  This led Johns Manville to maintain an appropriate nodule or tuft size, decreasing installed insulation air permeability. 

 

As explained in Owens Corning’s bulletin, “The bonded cubes did not nest well, leaving voids of relatively large air spaces and allowing R-value depleting convection to occur.”  This is why older loose-fill insulation had a problem with convective loops.  And it’s why modern loose-fill fiberglass product doesn’t.  They now use smaller chunks, nesting well together.

In summary, researchers at Oak Ridge National Lab found loose-fill fiberglass insulation 30 years ago had a problem.  As the attic temperature dropped, so did R-value.  It happened only with loose-fill fiberglass insulation they tested, though.  As a result, fiberglass insulation manufacturers took a good look at their product and found by using unbonded material in smaller chunks, this problem went away.

Sometimes people (usually those who sell other types of insulation) will refer to this Oak Ridge study as proof fiberglass doesn’t work at all, ever, in any circumstances.  This has always been an exaggeration because a flaw was found only in loose-fill fiberglass used in horizontal installations on an attic floor.

Manufacturers say they have eliminated this problem altogether by improving their product and their research proves they’ve gotten rid of this problem.  A lot of people know about this Oak Ridge study from something they heard from someone who heard it from someone else who heard it from their boss who talked to someone who learned about this at a conference in 1994 (Hmmm – sounds like social media).

Is your new barndominium in Climate Zones three and greater and have a dead attic space? If so, then loose-fill fiberglass insulation is going to deliver results you can depend upon.

Blowing Attic Insulation

Blowing Attic Insulation, Without Vapor Barrier, Below Roof Steel

A very common problem I see involves people not preparing their post frame (pole barn) buildings to adequately be insulated.

Reader NED in THURMOND writes:

“Thank you for your help. I’m in process of completing a pole barn project. It’s divided into three sections…living area, workshop, and garage. The size is 24 x 44. The outside perimeter wall is 2×6 frame with OSB and metal on the bottom and metal only in the top portion. The wall cavity is filled with unfaced insulation and poly on the inside. The roof is 8’ oc trusses with metal panels and no moisture barrier. 6 mil poly was applied to the ceiling joists. I wanted to insulate the ceiling, so I removed the poly and plan to install Sheetrock and blow in R-38 overhead. The building has a ridge vent and soffit vents in the eaves. Do I need a moisture barrier on the ceiling or will the blown in insulation suffice? What, if any problems do you anticipate? Thank you so much.”


Mike the Pole Barn Guru responds:

Here are some anticipated problems –

Without some method of condensation control beneath your building’s roof steel you are going to have moisture problems. Blown in fiberglass or cellulose insulation will lose their effective R value once they get wet. A practical solution will be to have closed cell foam insulation sprayed upon roof steel underside. Normal recommendation would be two inches thick however your local applicator(s) can give you their best input from experience. Make sure spray foam does not block either eave air intakes or ridge exhaust points. You can create a “dam” at eaves to keep blown in insulation from filling soffits, by use of ripping high R closed cell insulation boards. Again, make sure not to block incoming airflow (you need a minimum of least one inch of free area above insulation boards).

Planning a new post frame building? If so, I encourage you to take appropriate steps for your building to have future insulation installed. Yes, there will be some initial investment involved.However it will be so much less expensive to plan for it now than to wish you would have later.

 

Loft Storage Solutions, Insulation, and Home Insurance?

DEAR POLE BARN GURU: I like the idea of a 2-stall garage with second level for storage. Is a second level storage area more economical than increasing the square footage of the building? Lot less concrete. JOEL in INDEPENDENCE

DEAR JOEL: Only in rare instances is it more cost effective to go up, instead of out. Some of the determination will be what the actual use of the space will be. If all you are after is very light storage in the trusses with no need for a bonus room, then ordering a roof system designed to support what I will refer to as a “Christmas decoration” load. This will be less expensive than greater footprint (although not as convenient to access.

By Building Code definition a “light storage” load is 125 psf (pounds per square foot) live load, which is more than four times greater than a residential floor. If you are going up, then it is probably best to define the area as being a residential bonus room, unless you do intend to store every heavy items on the floor (e.g. stacks of books, engine blocks).

In my mind – I am always after practicality, so if it is worth storing, then it is worth having ready access to when I want – which makes my solution a larger footprint unless physical space dictates no other design solution.

 

DEAR POLE BARN GURU: If I were to use your reflective radiant barrier, can I also use batts fiberglass with it. If so, which product is put up first (I have a post frame building) and was thinking of putting the reflective attached to the underside of the purlins and then batts. If this can be done, I was looking for what goes up or in the cavity first, and if can be done, faced or unfazed batts. Thanks for any help. ROBERT in MCCAULEY

DEAR ROBERT: The CAN vs. SHOULD question.

You could place a reflective radiant barrier on the underside of the roof purlins, however it is only going to be effective at condensation control provided you can completely seal it. As the purlins most probably connect to roof truss, chances are it would be nearly impossible and most likely improbable to achieve the desired result.

As your building is already constructed, if it does not have a vapor barrier on the underside of the roof steel, then you should have closed cell foam insulation spray across the underside of your roof surface.

Provided your building’s roof trusses have been design to support the weight of a ceiling, and is adequately vented, you can use unfaced batt insulation across the attic floor, however blown in insulation will be far more effective and probably competitively priced.

 

DEAR POLE BARN GURU: Is it difficult to Insure a Pole Barn Residence in Michigan? Looking to build in St. Clair Michigan on approx. 5 acres. JOE in SPADA

Gambrel roof pole barnDEAR JOE: Due to the unfamiliarity of insurers with what a post frame (pole barn) residence is, maybe. What you are actually insuring is a wood frame residence, with whatever the choices of roofing and siding happen to be. Post frame construction is Building Code conforming and as long as you present it as a wood frame residence and it has been designed by a registered design professional (RDP – architect or engineer), you should not have an issue.

My own home is a post frame building of over 8000 finished square feet with three floors and two elevators and we have not had a single issue with obtaining insurance.

Which Insulation to Use?

Welcome to Ask the Pole Barn Guru – where you can ask questions about building topics, with answers posted on Mondays.  With many questions to answer, please be patient to watch for yours to come up on a future Monday segment.  If you want a quick answer, please be sure to answer with a “reply-able” email address.

Email all questions to: PoleBarnGuru@HansenPoleBuildings.com

DEAR POLE BARN GURU: We live in Texas. Can we use your configuration tool and have ya’ll create a plan for us? We will be building the barn ourselves.

If so, how much would the plan be for a 24 by 40 pole barn, 12 foot side walls, 6/12 roof pitch, one garage door, one personal door and 4-6 windows?

Thanks, Dan

DEAR DAN: We’d love to help you out with your proposed project – in fact it is what we do every day! Our system is totally geared to people who want to find the most savings as well as enjoying the pride of ownership which comes with a job well done.

Mike the Pole Barn Guru

DEAR POLE BARN GURU: We are undertaking a project of insulating our indoor riding arena/pole barn. We are installing the ceiling to the bottom of the trusses (got the ok from a structural engineer). We cannot decide what would be the best type of insulation to put in top of the ceiling. The choices: 1) spray foam, too toxic, too expensive. 2) blown cellulose/paper product-worried if it gets wet through the roof vent, worried that critters nest in it, worried that it blows around (from roof vent) 3) fiber glass – carcinogenic if you breath it in, while installing mostly, degrades through the years, critters can nest in it. 4) hard sheets of Styrofoam – like that it is solid, won’t rot if wet, won’t blow around, 4 x 8 sheets fit in between the trusses, don’t know if the “R” value is high enough or if it would insulate enough. We can’t decide what would be best. The ceiling is 29 gauge metal panels, looks like roofing. Question from Cindy in Warwick, NY

DEAR CINDY: Trying to insulate an indoor riding arena will literally be an undertaking and there is a strong possibility it will prove to be an untenable task just trying to heat the huge volume of space.

Before getting too deeply into your challenges, there needs to be a thermal break between the roof framing and the roof steel. If one was not installed at time of construction, the best choice might be to have a thin layer of spray foam placed on the underside of the roofing.

The other option would be to remove the roof steel, place the reflective radiant barrier and then reinstall – which could easily be quite an undertaking.

With the condensation problems solved, ventilation is the next step to tackle. If you have vented overhangs and ridge, it is probably adequate. If not, an entire new set of issues awaits you – as gable vents will become the only Code approved method of ventilation. If water is coming through your ridge vent, then it was done incorrectly (either wrong product, or poor installation) and should be replaced or repaired.

My recommendation is going to be blown in either cellulose or fiberglass. It is going to give you the highest R value per dollar. A professional installer can blow it in, removing the risk of you inhaling. In your part of the country you should probably be looking at as high as R-60. Once installed the probability of the insulation blowing around in your attic is small and even a nominal amount of settling can be handled by adequate thicknesses to begin with.

As far as degradation of blown insulation – we are talking about decades, not months or years. If you do blow in insulation and have vented eaves, be sure to place insulation baffles (cut from high R foam board) appropriately to keep insulation from falling into the overhangs. The baffles also allow an inch of clear net airflow over the top.

Mike the Pole Barn Guru

DEAR POLE BARN GURU: I want to submit two requests for quotes – one for a larger building and one for a smaller building – because I don’t yet know if the house I will decide to buy and renovate will have an attached garage or not.  If it does have an attached garage, then I would go with the smaller building.  If the house does not have an attached garage, then I will want to go with the larger building.  Both buildings would need a back overhead door for driving our trailered boat in through the back and out the front.   Both buildings would need one taller and wider opening for the boat and either one or two smaller openings for cars/equipment.  Both buildings would have wainscot, single-hung windows, all metal roof and siding, no skylights, eave lighting, ridge vent, etc.

I am thinking of a residential pole gable building garage/workshop combo for my husband’s home workshop, home lawn and snow equipment, 22′ boat on trailer, shelving storage, etc.

Can I submit more than 1 request for a quote on-line or would it be better to talk with a customer rep on the phone and/or submit drawings, or wait until I find the house that I am going to renovate in order to see if it has any attached garage?

Thank you,
Double Requests

DEAR DOUBLE: Some of the answer depends upon your goals. If you need some sort of budgetary figures only, to assist with your house purchasing adventure, then requesting multiple quotes online will be a quick way to get started.

Ultimately, until you have actually purchased a property, any preliminary information is going to be just what it is – preliminary. The best dictate for what you will eventually build will be determined by the property you will be building on.

Once you have an idea – you can get more than one quote either online, or by calling the toll-free number listed on the website – one of our building designers will be happy to assist you in your planning.

A caution – be sure to talk with the Planning Department which has jurisdiction over any property you are considering purchasing. There may be restrictions on what you will be allowed to build and it is best to find them out prior to signing the check.

Mike the Pole Barn Guru