Tag Archives: net free ventilation area

Help! My Barndominium Roof is Dripping!

Help! My Barndominium Roof Is Dripping!

Reader TIMM in WHITEFISH writes:

“Thanks for taking my question. I recently built a barndominium in NW Montana. I tried to find someone to build it for me, but the demand and cost in the area had gone up so much that I had to do almost all the work on my own. I was not completely unfamiliar with building but not an expert by any means but I was able to get it built with helpful videos found online. I finished the home in late October and have moved in. The home is 28’x36′ with 10′ walls and is all living space, no garage. I had planned on doing spray foam insulation around the entire shell of the barn and had hired a company in August to come out and spray the barn but they were not going to be able to get to the building until December at the earliest but we were willing to do it and fight through the winter in our camper. Our plumber mentioned a product to us that he had seen some other clients use called Prodex that had similar characteristics of spray foam with a reflective surface on both sides and it was something I could do myself and much sooner. I did some research and the product looked good and the reviews looked good so I bought some and installed it. The steel was already on when I installed it so the Prodex was installed by stapling or screwing to the Purlins/Girts around the whole building which was an install method on their website. While we were mudding/painting/texturing I noticed some condensation in the attic in between the steel and the Prodex insulation (I could see where it was coming through a seam in the Prodex). I asked some people and they thought it was just because I was putting a lot of moisture in the air that was causing the condensation and it would dry out when we were done. On a recent trip up to the attic I noticed that the steel is still condensating when it is cold outside and the Prodex itself seems to be condensating as well. I emailed Prodex and they told me that it is caused by cold air moving across the inside surface of the steel and I should put foam around the ridge cap, eave edge of roof and tops of wall. I have foam around the ridge cap, but nothing on the ridge cap ends, I have foam on the eave edge of the roof, but only in the high ridge parts, and I have nothing on the walls. I am also concerned that this is happening inside of the walls which may lead to a bad mold problem next summer. My question is, how do I get it to stop condensating? I am ready to do whatever I need to do. I just don’t want to throw ideas at the house until something works. As far as ventilation goes, I am sure I do not have enough but was hoping to address that in the summer months. I do not have eaves on the building which I regret so my only real ventilation is the ridge cap and the little bit that may be coming through the ridges on the eave edge of the roof. I thought about gable vents, but I felt like that would let too much cold air in and would make the issue worse, but maybe that is what I need? If I put in gable vents, do I pull out the Prodex insulation and leave bare metal on the inside of the attic? I am trying to figure out a way to reduce the moisture right away (dehumidifier?) while I work on a long term solution but I don’t know which direction to go to solve this issue. I thought about pulling off the steel and putting in plywood sheeting, but we are in the middle of winter and that would have to wait until Spring at least and I am afraid I will end up with too much water damage by then. I have even considered putting sheeting under the roof and replacing the outside walls with wood siding but the cost would be high and I feel like there should be a solution to this issue. For heat we electric wall heaters (Cadet in-set wall units) occasionally and a pellet stove most of the time. We put the Prodex insulation as well as blown insulation in the attic to about 12 inches deep and we put Prodex as well as rolled insulation in the walls for a total of about an R30 value. Dryer and bathroom vents both go outside and nothing is venting into the attic. Any help would be appreciated! Thanks.”

Mike the Pole Barn Guru says:

Kudos to you for doing a D-I-Y. Sadly you were lead to a product (Prodex) claiming to be insulation, however in reality it is a condensation control, and only if totally sealed.

All of these issues could have been easily addressed at time of construction had your building kit provider given you proper advice.

First thing to do is to get your attic properly ventilated – you need to add at least 121 square inches of NFVA (Net Free Ventilating Area) to each gable end. This will give you an air intake and your vented ridge will then function as a proper exhaust. By itself, this should greatly minimize, if not totally cure your problems.

As time allows, remove roof Prodex, have two inches of closed cell spray foam applied to roof steel underside, and increase thickness of blown in attic insulation to R-60.

If you do not have a well-sealed vapor barrier under your concrete floor, if possible, seal top side of it (this is where moisture is coming from).

Heating as much as possible with your pellet stove will also help to dry your interior air out and provided your slab is sealed, should help greatly.

I do have some concerns about your walls, if you have faced insulation batts with Prodex on outside of batts, you are potentially trapping moisture between two vapor barriers. If this is indeed your case, come Spring, remove siding (one wall at a time) , remove Prodex (as much as possible) and add a Weather Resistant Barrier (Tyvek or similar) to the exterior of framing, properly seal all wall openings and reinstall wall steel.

Building Codes and Requirements in Contract Terms

Building Codes and Requirements in Contract Terms

Disclaimer – this and subsequent articles on this subject are not intended to be legal advice, merely an example for discussions between you and your legal advisor.

Please keep in mind, many of these terms are applicable towards post frame building kits and would require edits for cases where a builder is providing erection services or materials and labor.

BUILDING CODES: The Total Cost of this Agreement is based upon an agreement between Purchaser and Seller, for Seller to perform according to a specific scope of work, per code and loading information as stated in the Agreement. Total Cost to Purchaser may be increased depending upon the review completed by one or more of Purchaser’s permit approval granting agencies, which include, but are not limited to building and land use departments, in which event either the Seller or Purchaser shall be relieved of further obligation under this Agreement if the increase in Total Cost is greater than ten percent (10%). 

In the event the building department, any other governmental agency or agent may require revision(s), further documentation, or explanation of any work after one initial plan check/review, Seller will advise the Purchaser of any required changes or modifications. Upon notification by Seller of extra work or materials required, Purchaser shall authorize Seller to perform such according to Section xx of this Agreement, “Change Orders”. 

Seller is not responsible for any plan check fees, re-inspection fees, special inspections, analyses or reports which are not ordinarily provided by Seller to a building department, plan check or inspector, including, but not limited to any additional charges resulting from unfamiliarity of said person(s) with either post frame buildings in general or the work as specifically designed by Seller. 

Once the approved plans and specifications have been reviewed by the applicable jurisdictions and building permit has been issued, both Seller and Purchaser may rely upon those approved plans and specifications as conforming to all applicable regulations and building codes of the jurisdictional building authorities. 

Total cost, unless otherwise specified, includes two sets of engineered 24″ x 36″ plans. Extra sets are available at time of order for $xx per set. Plans will be made available online (once drafted) and must be fully reviewed and approved by the Purchaser prior to deliveries being scheduled. Time spent handling calls or Emails made by the Purchaser, Purchaser’s agent(s), or Purchaser’s permit issuing agencies to engineer of record will be paid for by Purchaser, directly to the engineer, at engineer’s prevailing rate. 

In the event any conflicting information is found on the plans, Purchaser agrees to immediately notify Seller. Seller will promptly clarify or correct any conflicting information (at no charge to Purchaser), this being Purchaser’s sole remedy. 

Building Codes require attics above insulation to be ventilated with a net free area (NFVA) not less than 1/150 of area of space being ventilated. NFVA may be 1/300 of area of space ventilated, provided 50 percent of required ventilating area is provided by ventilators located in the upper portion of space to be ventilated at least 3 feet above eave, with balance of required ventilation provided by eave or gable vents. Purchaser to make provisions for adequate ventilation, if not so included in Agreement.

My commentary: permit issuing authorities can and will do some absolutely bizarre things. Often all it takes is one new person in a department who is fresh out of school and wants to prove their brilliance by upsetting an apple cart. This caps these unforeseen costs to both parties.

PER ANSI/TPI 1 LEGAL REQUIREMENTS MANDATE: In all cases where a Truss clear span is 60 feet or greater, the Owner (Purchaser) shall contract with any Registered Design Professional for the design of the Temporary Installation Restraint/Bracing and the Permanent Individual Truss Member Restraint and Diagonal Bracing. In all cases where a Truss clear span is 60 feet or greater, the Owner (Purchaser) shall contract with any Registered Design Professional to provide special inspections to assure that the Temporary Installation Restraint/Bracing and the Permanent Individual Truss Member Restraint and Diagonal Bracing are installed properly.

For extended reading on this subject, please visit: https://www.hansenpolebuildings.com/2019/09/responsibilities-where-the-legal-requirements-mandate/

Venting an Attic

Saving Money When Venting An Attic?

While some of you may think I have been doing post frame buildings since dinosaurs roamed our planet, I can assure you this is not true. Now my youngest son, when he was pre-school aged, did ask me (in all seriousness) what was it like watching space aliens build Egypt’s pyramids!

When reader DOMINIC in FESTUS wrote his question to me, it got me thinking about when I first had a client ask for a building with insulation at ceiling level. While I truthfully do not remember, in my first 6000 or so post frame buildings (we are talking 1980s here) I doubt there were more than a handful.

Fast forwarding to today’s modern fully engineered post frame buildings and nearly every building – garage, shop, barndominium, etc., is going to be climate controlled to some extent and most of these have enclosed attic spaces with insulation to be placed at ceiling level.

Here is DOMINIC’s question:

“I will be building a 30×40 pole barn soon. I plan on putting a ceiling in with insulation. My question is on attic venting. It seems best practice is to use a ridge vent with vented soffits but are gable vents alone sufficient? It would be cheaper for me to just do gable vents.”

Your best practice is to have even airflow from eave intakes to ridge exhausts. If your building will have sidewall overhangs, you might as well take advantage of this. You COULD (as an alternative) utilize gable vents. Provided at least half of your gable venting is located in the upper half of the attic, you can get by with as little as 576 square inches of NFVA (Net Free Ventilation Area). To achieve this would require (3) three 20″ x 30″ gable vents in each endwall. This could prove unsightly, difficult to install and is unlikely to result in being less of an investment than ridge vents. NOTE: a 20″ x 30″ gable vent provides roughly 106 square inches of NFVA (not 20″ x 30″ for 600″).

Of course, me being me, I had to snoop our records to see if he had requested a quote from us – and indeed he had…..

In looking over your quote from us, you may also want to consider increasing your overhead door width from 14′ to 16 (or even 18′) as you cannot safely get two vehicles side-by-side through a 14 foot wide door. For sake of resale value, with a 14 foot door it will appraise as a single car garage, wider doors will nearly double your appraised value as it is a two-car garage then.