Tag Archives: cladding

Dead Air as an Insulator

Dead Air as an Insulator

Are you considering building a climate controlled post-frame building? If so, then proper insulation is (or should be) at the top of your list.

Reflective InsulationIf you have not seen ridiculous claims of double digit R-values from reflective radiant barriers yet (aka ‘bubble wrap insulation”) you will. Read more about these claims here: https://www.hansenpolebuildings.com/2014/04/reflective-insulation-wars/

Reflective radiant barrier manufacturers base their R-value claims upon an assembly including a 100% sealed dead air space on one or both sides of their products. In all reality, it is impossible to achieve this in real world construction.

For many years buildings have been built with an air space between building cladding and batt insulation in wall cavities. This air space did, in fact, help circulate air inside the wall and ventilate humidity through the wall. Now, as we increase wall air tightness quality and increase insulation levels, this air space no longer serves a ventilating function. Being on modern heavy insulation outside, it is too cold to help much with ventilation, and convection currents in this air space can actually make condensation problems worse. In addition, this air space is not a very good insulator. It is now recommended that all space between inside wall finishes (such as gypsum wall board) and outside cladding be filled with insulation, leaving no air space. Again – when insulating an exterior wall, don’t leave any air space.

Improper installation techniques with batt insulation can cost you 20% of an exterior wall’s insulating value from air spaces in hidden corners. This radically increases thermal bridging through framing members.  If, on these same walls, you have an accidental space between insulation and vapor barrier, an air current can loop around insulation taking heat directly from warm interior finishes to cold cladding.

For an air space between wall insulation and interior finishes, vapor barrier location is critical.  If an air space is between insulation and vapor barrier, air will rise because of building warmth.  This air movement will find its way through or around insulation to cold side, where it will fall due to cladding’s colder surface.  When insulation completely fills space between wall girts this looping is minimal.  When insulation is installed less than perfectly, this looping force will accelerate.  If there are open triangular corner spaces as mentioned above, this becomes a pump moving heat from interior finish to cladding as if there was no insulation there at all. 

When there is an air space between vapor barrier and interior finish, nothing happens.  Temperature goes from cool on bottom to warm on top but air in this space has no access to cold exterior cladding.  It may circulate but it has no more effect than room air circulation. 

Years ago walls were constructed to leave an air space between exterior wall framing and interior finishes.  This was enough thermal break to stop condensation from forming on interior finishes in line with wall girts.  With modern construction and heavier insulation, there is no longer a condensation problem on interior finishes caused by girts being cold.  (There still is heat loss and in some climate zones building codes now actually require sheet insulation over all wall girts, either inside, or outside.)  An air space’s insulating value is very small compared to the same thickness of any insulation. 

Trapped air is an excellent insulator. Air moving freely carries heat. Circulating air, such as in a wall cavity, is effective at pumping heat from warm side to cold side. Not an insulator, in other words.

To be effective at isolating heat, air must be confined, trapped in tiny spaces, like in fibers of fiberglass, rock wool, or cellulose. Foam is particularly good at trapping air. So you take a not a very good heat conductor product and arrange for it to have many tiny cells able to capture air.

Wet Set Brackets, a Walkout Basement, and Rigid Foam Issues

Today’s Pole Barn Guru tackles reader questions about using wet set brackets on a stem wall foundation, if it is possible to build over a walkout basement, and the viability of installing rigid foam between framing and steel cladding.

DEAR POLE BARN GURU: Hey there guru. We are planning on building a post frame home next year. Now for my question/s. Is it possible to use wet set brackets for posts on a block stem wall foundation? I also had the thought of marrying posts with brackets to a conventionally anchored double sill plate? If using a pier and wet set brackets system… Can a person do a raised floor design? And if so how would one keep the bugs and critters out of the “crawl space”? BRAD in SWANVILLE

DEAR BRAD: Wet set brackets can be poured into properly engineered and constructed block, concrete or ICF stem walls. In order to resist uplift forces, brackets are best installed directly into top of walls, with a properly pressure preservative treated sill plate between columns to attach siding to.

When using a pier and bracket mounted column system you can most certainly do a raised wood floor (crawl space) design. Any crawl space would require encapsulation (read more here https://www.hansenpolebuildings.com/2020/11/11-reasons-why-barndominium-crawl-space-encapsulation-is-important/) by Building Code. A non-decaying barrier to prevent burrowing creatures would also be prudent (https://www.hansenpolebuildings.com/2012/06/rat-wall/). My recommendation (and we can show this on your engineer sealed plans provided with your building) would be to use 19 gauge, 1/2″ x 1/2″ galvanized wire mesh around your building’s perimeter to a depth of three feet. This can be done be means of a trench and will be far less expensive than pouring a wall between columns.

 

DEAR POLE BARN GURU: Can I put a walkout basement under a steel frame residence?
JEN in HARTFORD

DEAR JEN: While I would have no idea on what sort of engineering it would take to mount a PEMB (Pre-engineered Metal Building) to a walkout basement, fully engineered post frame buildings can be designed to incorporate a full, partial or walkout basement. Read more here: https://www.hansenpolebuildings.com/2020/02/barndominium-on-a-daylight-basement/

 

DEAR POLE BARN GURU: Hello, I am considering building a cabin using pole-construction. I was wondering is it possible to use rigid foam insulation between the outside of the structure and the roof/wall cladding? GILES

DEAR GILES: Placing rigid foam insulation board between framing and cladding is not structurally a good choice. Post frame buildings work due to shear strength of their ‘skin’. When a non-structural sheathing is added it allows for fasteners to deform between cladding and framing, reducing shear strength, causing elongation of holes in siding/roofing and potentially a failure condition. You would be better served to use two inches of closed cell spray foam on inside of cladding after your cabin is erected.

 

 

 

 

Looking for a Place for a New Barndominium

Looking for a Place for a New Barndominium

Reader PATTI in MINNESOTA writes:

My husband and I are knocking around the idea of doing a Barndominium. 

We need a 4-5 car garage space and we can barely afford a traditional preloved home that has a 3-car garage which will require us to add another stall or two onto an already taxing home price!

I’m optimistic that we can pull off everything that’s needed and hopefully within the budget!

I’m doing the bulk of the research and found your site to be so packed with worthwhile information.  I want to see what you’d be able to do for us to make this as seamless and headache free as possible?

I started looking for property and messaged the City Halls for the locations we want to see if they’d allow such a structure.  Not sure how to handle the siding issue.

Inver Grove Heights, MN 

Will consider it a single family home.  Needs to meet setback, height and doesn’t exceed allowed impervious surface for the lot.  

Exterior siding regulations require horizontal lap type siding or similar.  Vertical siding like a pole barn is not acceptable material.  

**** Is this even possible to meet this request or is there a way we can argue against it.  Any knowledge you can offer would be so helpful****

Rosemount, MN

“The structure would function as a single family home, and therefore the exterior materials would need to be complementary to a residential structure (no metal siding, etc.).  Additionally, the foundation would need to meet the building code requirements for frost footings.  Also, the zoning code regulates the size of attached garages as follows: The footprint of an attached garage is a maximum of 1,000 square feet but can be increased up to a maximum of 1,500 square feet so long as the garage does not exceed 50 percent of the gross floor area of the principal building (garage and living area combined).”

Farmington, MN

*Considers this Agricultural that would need a minimum of 40 acres, what!!!

****Is this common and is there anything we can do to fight this so we get this under a single family home that we could put on a .25 acre plot?****”

Mike the Pole Barn Guru responds:

Thank you for reaching out to us and for your kind words.

Planning Departments are an extension of a jurisdiction’s ruling body (city council, county commissioners) and have basically power of life and death. They can dictate footprints, heights, setbacks, type of cladding (roofing and/or siding), and even colors. They ARE limited to ordinances written by their ruling body, so if you do not hear an answer you like, ask for a copy of their written ordinance. If they cannot produce one, then it does not exist and can be disregarded.

One beauty of fully engineered post frame construction is a broad variety of siding and/or roofing options are readily available.

Inver Grove Heights – exterior siding is within their realm of control.  At www ighmn.gov go to “City Code” in the left hand menu list and click on it. Scroll down to Chapter 15, then 10-15-17. B.2 gives your options with steel being none of them.

Rosemont – you do not have to pour a concrete foundation to meet Code requirements for frost. You will have to insulate the perimeter of your building to at least four feet below grade, not a big deal and can be done with rigid insulation (this insulation is typical for any type of structure). If you erect a 3000 square foot (sft) building, as much as 1500 sft can be garage.

Farmington – you threw them off at “pole barn house”. You are building a fully engineered custom designed wood frame home. This should be allowable anywhere zoned for single family residences. You may have exterior appearance and footprint issues once they have gotten this into their heads as being a SFR (Single Family Residence).

You will find as you get farther away from Minneapolis and into county rather than city controlled areas, things tend to become more property owner friendly. You also might consider South Dakota as an option, as our Planning and Zoning restrictions are few and far between.

Wind Performance Updates for Metal Roofs and Metal Building Structures

Last April I was contacted by Mark Robins, Senior Editor at Modern Trade Communications. They produce a magazine titled Metal Construction News. At the time, Mark was preparing an article on “Wind Performance Updates for Metal Roofs and Metal Building Systems” for their June 2017 edition.
Mark had read my article https://www.hansenpolebuildings.com/2016/12/asce-changes-2017/ and as a result contacted me asking for editorial content for the Metal Construction News article. It is always flattering to be asked to contribute and I do my utmost best to provide valuable content.
Here is the input I supplied to Mark:
“The biggest impact to designers and installers of metal roofs from ASCE 7-16 will come in the attachments of cladding and flashings. ASCE 7-16 comes with upward revisions in the design pressures for components and cladding, in some cases more than doubling the pressures. Generally the attachments of trims such as rakes and fascias tends to not be spelled out on building plans, but is more often left to the discretion of the installer. Contractors should make certain the RDP (Registered Design Professional – architect or engineer) who has prepared the structural plans has called out specifics for the connections of all steel trims. Failure to do so could result in some unhealthy consequences to the builder in the event of a catastrophic event.

While, in my humble opinion, buildings should be designed to meet the latest and greatest requirements – there will be jurisdictions who are either slow to adopt the newer provisions, or who will opt to modify them without a clear understanding of what they are doing. The variability of enforcement from jurisdiction to jurisdiction will leave an unfair bidding advantage to those who choose to take on the risk of minimally designing their structures. Sales staffs should be made aware of the position their employers take and be prepared to sell to their clients the advantages of buildings constructed to the new, updated standards.”
I thank Mark Robins and Metal Construction News for the opportunity to be of service. The actual full article can be read here: https://www.metalconstructionnews.com/articles/winds-of-change.