Tag Archives: gable vents

R Panel Gable Vents

R Panel Gable Vents

“R” steel roofing and siding panels are typically used on all steel buildings where larger spans occur between wall girts and roof purlins. With a three foot width net coverage, these panels have a 1-1/4 inch tall high rib every 12 inches with two low stiffener ribs between. R panels do not have a full underlapping (or purlin bearing) underlap. This lack of a purlin bearing underlap makes this product both less expensive (as it can be roll formed out of a narrower steel coil) and more difficult to install. Without careful placement at laps, panels tend to “walk” with one or both panel ends covering more or less than the necessary three feet.

Very few all steel buildings make provisions for ventilation. Rarely do they include sidewall eave overhangs, leaving no place for an eave air intake through a vented soffit.

So, how to vent?

Reader STEVE in PHOENIX writes: “Mike,
Hello. I’ve been researching venting options for an existing clearspan type red steel metal building and was directed to your snap in style gable vents for ribbed metal panels.  My building is covered with R panel metal siding…..the high ribs are 12″ on center (pic attached). I’ve been working with Justine on selection and pricing of your gable vents.  Will your vent panels work with this siding and if not, do you have a venting solution for this building? Thanks.”

My reply:

R panels typically have 1-1/4″ high ribs. I do not believe the snap ring vents will work with ribs higher than 3/4″ (Justine can confirm). If not, then you could use a standard gable vent with a J Channel surround. Just like snap ring applications, cut the hole in siding for the vent (make it 1/4″ taller and wider than the vent you will push through the hole). Cut J Channels to fit the vent, with interlocking and overlapping corners (just like a non-integrated J Channel window). Insert individual pieces of J Channel into the hole, joining corners as you go. Slide vent into J Channel “picture frame” using lots of caulking between vent and J Channel and at each of the J Channel corners.


Snap ring vinyl gable vents (https://www.hansenpolebuildings.com/2018/07/vinyl-gable-vents-for-pole-barns/) make installation a breeze and can quickly be installed in post frame buildings with steel siding with ribs no higher than ¾” . When designing your new post frame building discuss ventilation with your Hansen Pole Buildings’ Designer at (866)200-9657.

Venting an Attic Without Soffit Air Intake

Venting an Attic Without Soffit Air Intake

Loyal reader KEN has an attic space with only air exhaust points – a vented ridge, and no air intake. His dilemma, how to adequately ventilate his attic without vented soffits.

Ken writes:

“I finally was able to make contact with the manufacturer of the open foam like material used under my ridge as a vent. The following is cut and pasted from their technical material: Net Free Area 1”nom.Thickness 8.5 sq.in.per lin.Ft.per side (17 sq.in .per lin.Ft.ridge).  Since I have a 60 foot ridge, that would equal 1020 sq. in. or 7 sq. ft. 

Given the ridge vent, do you still recommend 3 sq. ft.  venting on each end?

You note that an 18×24 would provide 140 sq in (or 0.97 sq. in.), but 18×24 is 432 sq in.  Do the louvers and other components reduce that by a factor of 3, just wanting to confirm.  With a 3 sq. ft. requirement, I would need a vent nearly 3 times an 18×24.  Maybe it just comes down to not the ideal but what can be practically installed. 

In order to prevent rust at the cut line, should I caulk the outside seam where the louver comes through the wall?”

Mike the Pole Barn Guru writes:

Another way of thinking about ventilation – view it like a straw. Obviously with best (and most) straws each end has an opening. What happens when a hole exists somewhere between ends? A reduction occurs in your ability to draw up water or soda. A similar effect happens when different vent types are employed over a shared air space.

Air and water are similar, their flow follows a path of least resistance. In a properly designed and installed attic ventilation system air flow travels from intake vents to exhaust vents, flushing out warm, humid air along roof deck (think underside of roof steel). However, if two or more different types of exhaust vents (gable and ridge) are used above a shared attic air space, one exhaust vent will likely to interrupt air flow to the other. In this arrangement it becomes another intake vent for a primary exhaust vent – leaving large sections of attic space incorrectly vented.

I would be inclined to seal ridge vent off and utilize gable vents. Dimensions of gable vents are overall unit dimension, not net free area (reduced from overall size by both exterior framework and louvers). Each endwall may require multiple vents in order to achieve an adequate airflow.

Caulking cut edges of endwall steel would certainly not hurt. A suggested caulking would be TITEBOND Metal Roof Translucent Sealant.

 

 

 

My Pole Barn Needs Ventilation

My Pole Barn is a Sauna in Summer- and needs ventilation!

“Hey there Pole Barn Guru, got a question about ventilation.

Just bought a house with a pole barn on the property. I believe it’s only about a year old. 30 x 32.  It has no soffits or windows, only a standard garage door and walk-in door.

Metal siding and roof, and the underbelly of the roof has a vapor barrier. There are also two ceiling fans in here.

I don’t care that it’s cold inside the building in winter, but it’s like a sauna now in the summer.  I was thinking of an exhaust fan to pull out the heat, but I don’t know if that’s waste of money. How does one ventilate this thing without having to bulldoze it and start over?

Thanks.

Dezy”

Mike the Pole Barn Guru responds:

Since you cannot increase the amount of venting in your soffits (as you have none), you’ll need help from power vent fans.

Attic vent fans can be hard-wired and equipped with a thermostat and/or humidity sensor so they automatically cut on at a preset moisture level or temperature. You could also install solar-powered attic vent fans, though it has been found most solar models aren’t powerful enough to be very effective.

To determine what size power vent fan(s) you need for your attic, you first need to know the size of your attic in square feet.

Attic Size

To determine the size of your attic, multiply the width by the length of the attic floor in feet. In your case 30′ wide x 32′ long = 960 square feet of attic space.

Vent Fan Size

Next, multiply the square feet of attic space by 0.7 to get the minimum number of cubic feet of air per minute the fan should be rated to move. 960 sft x 0.7 = 672 CFM minimum fan rating.

Add an additional 20% (CFM x 1.20) if you have a steep roof, and 15% (CFM x 1.15) for a dark roof. Attic vent fans are commonly rated from 800 to 1,600 CFM, making one fan suitable.

Vent Fan Location

Install gable mounted fans on the gable vent at end of the building facing away from the prevailing winds.

Intake Air Vents

It’s also important to have plenty of soffit or gable vents for the fan to draw air into the attic. To find out if you have enough vent space, divide the cubic feet of air per minute the fan(s) is rated for by 300 to come up with the minimum number of square feet of intake vent space needed for that size fan. 672 CFM ÷ 300 = 2.24 sq. ft. intake vent area

If you prefer the answer in square inches rather than square feet, multiply the answer by 144 and round to the nearest inch (2.24 x 144 = 322.56 sq. in. vent area).

 

Mold in a Post Frame Building Attic

Hansen Pole Buildings’ client BRENT in WASHOUGAL writes: “We have your 40×80 pole barn built sept. 2014, and it’s having problems with mold forming over the purlins. I’m wanting to know my options to prevent a future problem.

Thanks.”

Mike the Pole Barn Guru responds:

First – get rid of the mold. Mix in the ratio of one cup bleach per gallon of water and use a hand pump sprayer to saturate all moldy surfaces. You can also use a scrub brush to remove the existing mold.

The most common causes of attic mold are leaking roofs, inadequate ventilation and too much humidity in the building itself. If your concrete floor has a vapor barrier underneath it and/or is well sealed, you are probably not drawing in excess moisture from underneath the building – so we will look at the first two.

Mold showing along the tops of the roof purlins and not on the trusses, as well as the streaks down the sides of the purlins leads us to believe you may have screws which were inadequately placed. Screws which are not properly seated so as to compress the rubber washer, will leak. Screws which are driven in at an angle will also cause leaks. The roof should be investigated screw-by-screw to make sure all screws are properly driven. Water leaking around a screw shaft will eventually cause decay of the wood around the shank, so if screws cannot be tightened they should be replaced by a larger diameter and longer screw – in your case a #14 diameter by two inch long part.

Ventilation – in an ideal word your building would have had enclosed vented eave overhangs of 18 inches or greater on both sidewalls for an air intake, as well as a vented ridge to provide an exhaust point. This ventilation system provides for even airflow from eave to ridge throughout the entire attic area. Gable vents can be used to meet Code requirements for ventilation, however the reality is they are not very effective in providing ventilation other than near each end of the building’s attic. The Code requirement would be for 1/300th of the footprint area of the attic to be provided for as net free area of venting, as long as at least 50% of the venting is in the top half of the enclosed attic space. With a 40′ x 80′ building, you have 3200 square feet of footprint, which would require at least 10.67 square feet (or 1536 square inches) of net free ventilating area. To give an example a Mid America (www.midamericacomponents.com) Classic Rectangular vinyl vent 20 inch by 30 inch provides 297 square inches of net free ventilation area, so it would take three of these in each endwall just to meet the requirements of the Code!

There also is a difference between meeting Code requirements and what actually works in a real life situation.

Since you cannot increase the amount of venting in your soffits (as you have none), you’ll need help from power vent fans to exchange the moist air in your attic for dryer, outside air. Attic ventilation fans would help move the moist air out of the attic without giving it time to find a home on the purlins and trusses.

Attic vent fans can be hard-wired and equipped with a thermostat and/or humidity sensor so they automatically cut on at a preset moisture level or temperature. You could also install solar-powered attic vent fans, though it has been found most solar models aren’t powerful enough to be very effective.

To determine what size power vent fan(s) you need for your attic, you first need to know the size of your attic in square feet.

Attic Size

To determine the size of your attic, multiply the width by the length of the attic floor in feet. In your case 40′ wide x 80′ long = 3200 square feet of attic space.

Vent Fan Size

Next, multiply the square feet of attic space by 0.7 to get the minimum number of cubic feet of air per minute the fan should be rated to move. 3200 sft x 0.7 = 2240 CFM minimum fan rating.

Add an additional 20% (CFM x 1.20) if you have a steep roof, and 15% (CFM x 1.15) for a dark roof. Attic vent fans are commonly rated from 800 to 1,600 CFM, making one fan suitable for attics of up to around 1160 square feet, even with a steep, dark colored roof.

Vent Fan Location

Install gable mounted fans on the gable vent at end of the building facing away from the prevailing winds.

Intake Air Vents

It’s also important to have plenty of soffit or gable vents for the fan to draw air into the attic. To find out if you have enough vent space, divide the cubic feet of air per minute the fan(s) is rated for by 300 to come up with the minimum number of square feet of intake vent space needed for that size fan. 2240 CFM ÷ 300 = 7.47 sq. ft. intake vent area

If you prefer the answer in square inches rather than square feet, multiply the answer by 144 and round to the nearest inch (7.47 x 144 = 1075.2 sq. in. vent area).



 

 

Minimizing Condensation When Building Over an Existing Foundation

Minimizing Condensation When Building Over an Existing Foundation

Reader ROSS writes:

enclosed overhangs“Hello, I have a question about venting of my building. I currently am in the process of building a shop myself. I had an existing foundation of 75 x 42 that had 8ft concrete walls all the way around. I’m building my building on top of this to give myself 17’ sidewalls. My concern is about my venting. I’m planning to have soffit installed along the building and am not sure if I should go with Gable vents or ridge vents. The building will be insulated with 3” fiberglass with a poly vapor barrier on the walls and with 1” 4×8 sheets of foam board on the roof with all the joints taped. My concern with ridge vent is will moisture condense on the exposed ridge cap and drip since it has to be left uninsulated for venting or will it be ok? I would rather not have any drips. My gut feeling tells me I need to have plenty of venting since 3 sides of the concrete are covered with dirt and already show condensation pretty regularly when the temp changes. With my soffits do I need to run vented soffit the full length of the building? Thanks your response will be greatly appreciated!”

Mike the Pole Barn Guru Responds:

I’d start with excavating around the foundation and properly sealing it from the outside, as well as sealing the slab floor. It sounds like you propose to place foam insulation board between the roof framing and the roof steel – not a good structural idea, as you are significantly reducing (if not eliminating) any shear strength afforded by the steel panels, as well as eventually contributing to leakage from the screws being able to “work” between the framing and the steel. You would be ahead to either use a radiant reflective barrier (less expensive, more labor intense) or Condenstop/Dripstop (read more here: https://www.hansenpolebuildings.com/2014/07/condenstop/) beneath the roof steel. Either one of these products can be adhered to the ridge caps as well.

The Building Codes do not allow for gable vents to be combined with eave or ridge vents. Your best bet is to run full vented soffits on both eaves, combined with ridge vents the entire building length. https://www.hansenpolebuildings.com/2014/02/pole-building-ventilation/

 

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

Pole Building Ventilation

Ridge vent without soffit vent

One of the most overlooked areas of pole building construction is proper ventilation. Lack of proper pole building ventilation becomes even a greater issue when an enclosed attic space is present. The International Building Codes require any dead attic space to be ventilated. Without adequate ventilation, moisture from condensation will begin to accumulate on top of the ceiling. Mold and mildew can form on the underside of the roof sheathing and on the roof trusses.

One of the least expensive options for a new pole barn, especially with steel roofing, is to have a vented ridge. Very easily installed at time of construction, if there is ever a possibility of a flat, level ceiling being installed in the building, a vented ridge is a must.

A ridge vent without a soffit vent doesn’t work, and here’s why. By virtue of their design and location on the roof, ridge vents are predominantly exhaust devices. Warm moist air from inside the building rises, passes through the ceiling material and attic insulation and out through the highest point – the ridge.

The attic space will get makeup air to replace the air the ridge vent has exhausted along the path of least resistance. If there is plenty of soffit venting and if you have a relatively tight ceiling, then the makeup air will come from outside, which is desirable, summer and winter. However, without soffit vents, the makeup air comes from indoors, a situation which is not desirable in any season.

So what to do if you have a building with an attic space, and little or no ventilation?

attic ventilationIf mold is already a problem, scrub the affected areas with a diluted bleach and soap solution. Once clean and dry, a mold resistant paint can be applied.

I’ve heard others suggest a roof design without ventilation, an issue that is volatile and multifaceted. Basically – doing away with the dead air space in the attic. As I see it, the choice to go or not to go with attic ventilation does not in itself ensure good performance. The bottom line with attic assemblies, whether vented or not, is that they be done properly.

Filling the attic space with cellulose insulation may be an option, although expensive and is not a 100% guarantee to solve the problem. Cellulose insulation is dense, blocks airflow and contain salts which inhibit mold growth. In my opinion, many of the innovative uses I’ve seen for cellulose are experimental, but those experiments seem to be working well. If conditions permit, you could find a way to blow in cellulose at the gable ends of the trusses. Better yet, you could fill the truss cavity from the ridge. In any case, with cellulose insulation as a “total fill”, I recommend the use of a vapor barrier, such as plastic sheeting on the underside of the trusses and/or ceiling joists or a vapor-barrier paint applied over the drywall.

Only without a dead air space should a ceiling vapor barrier be utilized.

Maintaining low indoor humidity may be also effective, but it may require wintertime humidity below 25%, which could be uncomfortable, as well as near impossible to achieve.

Add Pole Building Ventilation.

If your pole building does not have enclosed vented overhangs, it may be possible to add ventilation along the top of the building sidewalls. However, each individual case should be examined, as drilling holes or cutting into a structural member could compromise the building’s integrity.

If a continuous ridge vent is not present, install one. Make certain there is a clear air flow from the attic space through the ridge – which may entail the removal of any sheathing (oriented strand board – OSB or plywood), vapor barriers, or other insulations directly beneath the ridge.

Although the newer versions of the Code prohibit the combination of gable vents and ridge vents, gable vents may be installed in each end of the building – to provide an intake for outside air.

The real solution – is to build it right in the beginning. Prudent design with vented soffit overhangs and a vented ridge may involve some initial investment, but prove to be an insignificant cost over the life of the building. And trust me, no one I’ve ever talked to had a “fun” time dealing with mold.

Dear Pole Barn Guru: Ventilation for an Old Pole Barn?

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: I am getting ready to insulate and heat an older pole barn so I have signed up here for some help and advice. So, I have an older pole barn that really has no eave/soffit vents or ridge vents. It’s pretty crude built. I want to insulate and add a ceiling. My concern is condensation in the attic after insulating. I plan on adding some sort of full ridge vent. Then I need some eave venting or add gable vents. The idea of adding gable vents makes me nervous because I don’t know how to seal them properly with the ribs in the metal siding. I will attach pics. Is there a way I can build in some eave vents? The metal roof just comes down the sides of the barn and there is an air gap between the rood and the siding that is covered by the white trim/flashing as seen in the pictures. Any ideas on what to do with this old barn before I start finishing it would be a big help. I also thought about attic fans in the ceiling. CB MAN

DEAR CB: You asked for advice, so here it is….your old building has some challenges when it comes to attempting to heat. The ventilation issue is just one of many. The building has no insulated vapor barrier under the roof steel to prevent condensation, which you have touched upon. Two other factors, either of which could be deal breakers – the building has horizontal sliding doors, which are impossible to properly insulate and seal, without them becoming permanently affixed, and the roof trusses are probably not designed to support the weight of a ceiling.

With all of this said, you have two really good solutions – the least expensive is to just put up another new pole building, designed properly to be climate controlled, using your existing building for cold storage. The other – knock this building to the ground and rebuild at the same location.

Assuming you may not be interested in either of these, and want to pour lots of money into a building you refer to as “crude built”; I will give you some solutions.

Toughest first – the trusses. As they are prefabricated wood roof trusses, there should be a manufacturers stamp on every truss. The design loadings might be stamped on the trusses (due to the age of your building the “might” is the operative word). With this information and the location of your building, I could probably give you an idea as to adequacy. If the truss manufacturer’s name can be found – see if they are still in business. If so, they can determine adequacy for you (for a small fee) and get an engineered repair if they are not adequate. If those fail, hire a registered engineer to do an evaluation for you.

Condensation under the roof steel…as the steel is nailed on, it cannot be removed and an insulated vapor barrier (something like A1V reflective insulation available from www.buyreflectiveinsulation.com) added. The best solution is probably going to be to spray foam insulate the underside of the roof steel.

Adding a ceiling – with the trusses verified for the ability to take the load (and correctively upgraded if needed), 2×4 ceiling joists can be placed between the bottom chords every two feet, with LU24 or similar joist hangers at each end.

Screw on 5/8” Type X gypsum board to the underside of the ceiling joists and trusses (it won’t span four feet, so don’t even attempt to). Leave an attic access hole somewhere close to the center, so insulators can blow in the desired thickness of insulation. Do NOT place a vapor barrier between the ceiling drywall and the framing above.

Ventilation – the new codes do not allow for gable vents to be mixed with eave and ridge vents. It is…use one or the other. Take the square footage of the footprint of your building, and divide by 300. This gives the net square inches of ventilating area which must be provided in each gable end of the attic. Hansen Pole Buildings has vinyl gable vents, in a myriad of colors, with snap rings. A hole is cut in the steel (using the snap ring as a template), the vent is pushed through from the inside, and the snap ring is then pushed on from the outside (this is a two person job). These vents are designed to accommodate ribs on steel panels.

Now the roof is taken care of, the walls are the next challenge. Remove the sliding doors and frame the openings down in size to fit insulated steel sectional overhead doors. You may be able to salvage the steel off the sliding doors, and if done carefully, use the pieces to fill in the gaps.

Again, the nailed on wall steel becomes a limiting factor….spray foam for the walls is probably the best solution. Keep in mind, you will need to put either drywall or a steel liner panel on the inside of the columns, as Code does not allow spray foam to be left exposed to heated areas.

Good luck – and let me know what choice you make and how it turns out.

DEAR POLE BARN GURU: We just made a phone call to Menard’s to order over a hundred bags of blown-in cellulose. While talking to the guy in the building department, he asked if this is for a pole barn, Told him yep. He then strongly emphasized to NOT use blown-in cellulose above the metal ceiling because the flame retardant material will rust and eat up the ceiling. This is the first I have heard of, so I did some quick research online and it looks like they have some kind of acid that act as a flame retardant.

Right now, our 30×48 gambrel pole barn with loft are being built. The shop will be finished with R-19 fiberglass in the walls and then T1-11 panelings will be installed. The ceiling is going to be a metal liner, obviously. The loft will be used for storage and man cave, so half of the loft would be finished in the future. There will be Low-E condensation barrier below the roofing, so the contractor told us there is no need for a vapor barrier in the shop ceiling where I would be blowing the cellulose.

Right now I am not sure what to think. Several months ago I did some research and have decided to plan on blown-in cellulose. Is this something I should be concerned about? What should I do to avoid the rusting issue the guy told me about? BTW, he told me to instead use blown in fiberglass which is something I am not thrilled about. Thanks. PERPLEXED

DEAR PERPLEXED: If the fiberglass and cellulose insulation people would spend more time promoting what each of them do as good, and less time shooting broadsides at each other, life would be so much better and they would probably each sell more product.

There have always been concerns about insulation causing corrosion when in direct contact with metal building components such as sweaty pipes, electrical wires or metal boxes, etc. Consequently, ASTM (American Society for Testing and Materials) standards for every insulation material contain testing which specifically addresses these concerns. In addition, in 1979, the CPSC (Consumer Product Safety Commission) promulgated a law, which regulated the fire and corrosive characteristics of cellulose insulation. A statement of compliance with these requirements is required on every bag of cellulose insulation. The types of metal tested with all insulation materials are copper, aluminum, steel, and additionally in Canada, galvanized steel. The test requires placing soaking-wet cellulose insulation with an imbedded .003-inch thick metal coupon inside a humidity chamber under conditions that are ideal for promoting corrosion. After 14 days, the metal coupons are removed, cleaned, and examined under a light to detect the smallest pinhole. In all, there are two coupons of each metal and all must be free of even one pinhole. This is a very strict test!

My recommendations are to make sure your attic area is adequately vented (no less than 1/300th of the attic footprint area in venting, provided at least ½ of the vent area is in the top ½ of the attic), make sure the insulation stays dry (no roof leaks), and do not have a vapor barrier between the ceiling and the insulation. Whether you choose fiberglass or cellulose, either should be fine.