Tag Archives: unfaced insulation batts

Temporary Client Insanity – Truss Problems?

Temporary Client Insanity – Truss Problems? 

Long ago someone told me during the course of any construction project there comes a time when every client goes absolutely bat-pooh crazy. Personally, even knowing what I know, I am guilty of freaking out and having had a case of temporary client insanity during our own remodel and construction projects for our home.

For hyperventilation they have people breath from a brown paper bag, in my case – perhaps a plastic bag over my head and tied tightly about my neck would have been more appropriate.

Below I will share a client’s concerns. He remained much calmer (totally appreciated) during this process than I might have. He wrote to Justine (Hansen Pole Buildings’ Master of All Things Trusses):

“Justine, one more thing, the top chords of the trusses show 2×8 and the trusses were delivered with a 2×6 top chord, so all the bracing (purlins) will be hanging down. This roof is going to be insulated.

Also, the double trusses are not fastened together and I think I should have more than 1 set of scissored trusses.”

Our Technical Support response:

Building plans are drafted prior to receipt of truss drawings, so trusses as drawn on your plans are merely a depiction of what they may look like. Top and bottom chords as well as internal diagonal webs may be entirely different. The roof slopes will be accurate. Your building’s roof purlins certainly may hang below roof truss top chords, as this has no bearing upon your ability to insulate (please refer to Figure 9-5 of your Hansen Pole Buildings’ Construction Manual). As your roof has a Reflective Radiant Barrier, if you intend to use batt insulation between purlins, make sure to use unfaced insulation without a vapor barrier on underside, otherwise moisture can become trapped between two vapor barriers. This can lead to ineffective damp insulation as well as potential mold and mildew issues.

Per change order #3 your building is to have standard trusses in front 24 feet and a vaulted ceiling in rear 24 feet. With a pair of scissor trusses at 12 feet in front of rear endwall, this allows for the rear 24 feet to be vaulted and front 24 feet to have a level bottom chord.

Truss assembly people are not carpenters – and rarely do truss manufacturing facilities even have nail guns. It also avoids nail wounds from inexperienced or inappropriate use. As an example – back in 1979, I was shopping for a new employer designing and selling trusses. I interviewed with Tilden Truss, near Seattle. They used air guns firing a “T” staple to initially set steel truss plates. Their fabrication shop ceiling was covered with hundreds (if not thousands) of these “T” staples!

You will find it much easier to maneuver single trusses around your building site, than twice as heavy double trusses.

Please feel free to address any building assembly concerns to TechSupport@HansenPoleBuildings.com.

Another crisis averted.

Do Vapor Barriers Trap Moisture?

Vapor Barriers Trap Moisture?

Do vapor barriers trap moisture in walls of post frame buildings? They can, but only if they are installed on both sides of a wall insulation cavity.

Regular readers of this column will recognize a prevailing trend towards climate controlling both new and existing post frame buildings. An ability to control interior climate extends far beyond merely what one happens to be doing for insulation. It also includes what one does for weather resistant barriers and vapor barriers.

Insulating WallsThe purpose of a vapor barrier is to stop warm, moist, indoor air from infiltrating fiber-type insulation (think fiberglass or cellulose) during cold weather and condensing. Visible moisture or frost on the inside of a vapor barrier is either caused by a leaky vapor barrier or moisture migrating into the wall cavity from the outside. Leaky siding can cause this, and it often happens in basements that are apparently leak free. Vapor barriers are essential for any kind of insulation that air can pass through. Never do the really foolish act of slashing a vapor barrier that you find has moisture behind it or forgetting to install a vapor barrier in the first place. Today’s best vapor barriers prevent moisture from moving into wall cavities while also letting trapped moisture escape.

Recommendations below are for cold-climate construction. As a rule of thumb, if you have to heat your building more than cool it, this probably applies to your circumstance.

A weather resistant barrier (https://www.hansenpolebuildings.com/2016/01/determining-the-most-effective-building-weather-resistant-barrier-part-1/) will prevent moisture from entering a wall from outside of building. It also allows any moisture within a wall to exit. Pretty slick stuff, as it is smart enough to be directional.

Inside of this wall, once unfaced (recommended) insulation batts are installed, should be a vapor barrier (https://www.hansenpolebuildings.com/2017/11/vapor-barriers-post-frame-construction/). It is imperative this vapor barrier not have unsealed tears or holes. It should be sealed to floor and ceiling and any joints, rips or tears should be adequately taped. Where problems most often occur, with vapor barriers, is when penetrations are made for things such as electrical boxes. Properly sealing of these penetrations with closed cell spray foam from a can does more to prevent warm moist air to pass through into your post frame wall insulation cavity, than anything else.