Tag Archives: International Energy Conservation Code

How to Pour a Slab on Grade

How to Pour a Slab on Grade in an Existing Barndominium

Reader PAUL writes:

“I have an opportunity to purchase a barndominium that has the posts set in 20” wide 40” deep peers. Unfortunately the county where this is located does not require a footing. All city codes in this area require an 8”X 36” footing. What solutions do you recommend for pouring the slab now that the shell has been erected?”

Most post frame buildings have shells erected then slab poured, so this should not be an issue. A pressure preservative treated splash plank should be in place around this building’s perimeter. It will become forms for your slab. Snap a chalk line on the inside of splash planks up 3-1/2″ from bottom, this will be top of your slab.

In Climate Zones other than 1 through 3, you will need to frost protect the building perimeter. This can be done by trenching around the edge of the building to required depth – 24″ in zones 4 and 5, 48″ in 6 and greater. It is usually easiest to install R-10 rigid insulation on the inside of the splash plank, with top of insulation even with top of slab to be poured. This also precludes any need to UV protect vertical insulation.

Depending upon how the site was prepared, you may need to excavate inside of this building. 

If in “frost country” a sub-base 6” or thicker should be first placed across the site. To maintain frost-free soils sub-base should be such as no more than 5% (by weight) will pass through a No. 200 sieve, and it is further desired no more than 2% be finer than .02 mm.

Prior to pouring, 2” to 6” of clean and drained sand or sandy gravel is spread below where concrete is to be poured. Mechanically compact fill to at least 90% of a Modified Proctor Density, otherwise slab could sink.

In areas prone to subterranean termites treat prepared soil with a termiticide barrier at a rate of one gallon of chemical solution per every 10 square feet.

Install a good, well-sealed 15mil vapor barrier below any interior pour, to stop moisture from traveling up into the slab through capillary action. Overlap all vapor barrier seams by a minimum of six inches, then tape. Vapor barrier should extend up column sides and to splash plank top. 

Minimum R-5 (R-10 being preferred) insulation shall be provided under full slab area of a heated slab in addition to required slab edge insulation R-value for slabs as indicated in International Energy Conservation Code (IECC) Table R402.1.2 Footnote (d).

In most instances, over properly compacted fill, 15 psi (pounds per square inch)  EPS (expanded polystyrene) or XPS (extruded polystyrene) insulation has adequate compressive strength to support a five yard dump truck on a nominal four inch slab on grade.

Consider this: 15 psi equals 2160 psf (pounds per square foot), making this greater than assumed compressive strength of most soil types.

If not using fiber-mesh or similar reinforcement additives to concrete mixture, place rebar (reinforcing steel rods) in slab center to add rigidity to concrete to aid in minimizing cracking.

Barndominium Spray Foam Insulation

What Amount of Barndominium Spray Foam Insulation is Adequate?

Reader DON in LAKE CHARLES writes:

“Building new pole barn. Would using closed cell foam in roof and walls be adequate?”

Lake Charles is in climate zone 2A. 2018’s International Energy Conservation Code prescriptively mandates (for your zone) a minimum R-38 value for ceilings and R-13 for wood framed walls. This would require 5-1/2″ in roof and 2″ in walls. You could go with 2″ of closed cell directly to underside of roof deck plus 6″ of open cell, or 2-1/4″ of closed cell with 5-1/2″ of Rockwool as alternatives.

Your state’s Energy Code for Insulation is what your insulation contractor and inspector are looking at, as well as International Building or Residential Code to prescribe what insulation material is safe and efficient to insulate your home. These two codes are used, specifically for prescriptive code, to base how much insulation you need, how it has to be installed, and what insulation materials can be used in certain areas and at what depth. It’s important to note each state has its own insulation code varying depending on climate zone.

You can meet code without having to worry about prescriptive R-Value numbers, through performance.

Performance is more complicated to pass code because your insulation contractor needs to prove his or her insulation creates an air seal, it has an aged R-Value, as well as several different variables. Basically, your insulation contractor is showing your inspector based on numbers and results from testing your insulation will perform efficiently and will also be safe.

Air barriers created by spray foam creates isn’t covered by prescriptive codes, however it passes performance. This is because closed cell spray foam’s air barrier prevents air leakage into and out of your home.

Traditional insulation, like cellulose and fiberglass, will meet prescriptive code when it comes to R-Value, but they still allow for movement of air into and out of your home. This leads to uncomfortable rooms and low energy efficiency.

So, an inspector can’t just take an insulation contractor’s word for it when it comes to how an insulation material performs. This is where testing comes in to help.

Most common way to check a home’s performance is to take all insulation data, room assemblies, etc. and plug those numbers into a computer program.

REScheck is a most popular and common program used when it comes to testing performance. It is so popular because it is fast and easy and once you enter your data, it immediately tells you whether you have passed or failed.

There are other programs out there tending to be more complicated, but are also considered more prestigious.

HERS Index is a measurement of a home’s energy efficiency. HERS is currently a more popular program for checking performance. Many homeowners want a HERS rating for their home because when they go to sell it this rating adds extra value.

Concrete Slabs on Grade for Cold Climates

Concrete Slabs on Grade for Cold Climates

My lovely bride and I have a shouse (shop/house) in Northeast South Dakota, where it can tend to get chilly in Winter. Reader TERRI in DULUTH is in a similar situation and writes:

“What type of slab for cold climates do you recommend?”

Well Terri, thank you for your patience in awaiting a response, your email address was not included with your question, so I was unable to message you back as quickly as I would have liked.

PLEASE – If writing an “Ask the Pole Barn Guru” question include your email address.

Injecting some humor (sadly, I have to point it out as not everyone gets it) – I would recommend a concrete slab.

Before diving into this subject – accept one fact, concrete slabs will crack. If you are expecting otherwise, you are setting yourself up for disappointment.

First key to a successful slab is excellent site preparation: https://www.hansenpolebuildings.com/2017/02/building-site-preparation/

Second – insulate your slab’s perimeter. 2021’s International Energy Conservation Code (IECC) provides guidance to meet energy code requirements for every county within our country. Begin by looking up your Climate Zone: https://codes.iccsafe.org/content/IECC2021P1/chapter-3-re-general-requirements

I will cheat and tell you Duluth (St. Louis County) is climate Zone 7.

Scroll down to Table R402.1.3 to find Insulation Minimum R-Values.

In Climate Zone 7 your slab perimeter must be insulated to R-10 and be four feet in depth. 

Weirdly enough, Minnesota’s Building Code only requires footings to be at 60 inches of depth in your area (https://www.revisor.mn.gov/rules/pdf/1303.1600/2015-01-23%2012:37:31+00:00). 

Although actual frost depth in your area is more like 80” in depth:

I would probably look at augering holes no less than 72 inches in depth, using a bottom collar of 18 to 24 inches (per your engineered building plans). This would allow you to trench between building columns and install R-10 rigid insulation along your building’s perimeter to a depth of four feet.

If you are going to do radiant in-floor heating you should be placing R-10 beneath your slab and on top of a vapor barrier of no less than 6 mil visqueen (I prefer 15 mil thickness to reduce chances of perforations during pouring).

Insulated Bookshelf Wall Girts

While we United States residents like to think of ourselves as perhaps the center of our universe, post frame construction appears world wide.

Reader JONATHAN in HALIFAX picked Alabama as his state when he filled out his online request for information when he wrote:

“What insulation do you suggest between bookshelves of wall?”

With so many post frame buildings being used for residences, commercial buildings, shop/houses and barndominiums, properly addressing how to insulate has become of utmost importance.

I am going to take a stab and guess your Halifax is in Nova Scotia, rather than Alabama. My lovely bride and I made a stop there on a cruise from New York City a few years ago – beautiful area (and I got a Harley-Davidson T shirt).

If so, you are in what would be an equivalent to our IECC (International Energy Conservation Code) Climate Zone 7. For wood frame walls, this would require an R-20+5 or R-15+10, where your plus value is for continuous insulation.While continuous insulation is most often usually on exterior of framing, Martin Holladay – editor of Green Building Advisor feels confident in it working as well on inside of framing. Given this, I would put a Weather Resistant Barrier (https://www.hansenpolebuildings.com/2016/01/determining-the-most-effective-building-weather-resistant-barrier-part-1/) between wall framing (bookshelf wall girts) and siding, then fill your cavity with rock wool (as it is not negatively affected by moisture), then use rigid foam insulation inside of your framing. You can glue these sheets to your framing (bookshelf girts) to eliminate any thermal bridging from fasteners and then glue your interior finish to it. Make sure to tightly seal your rigid foam boards and to caulk along the bottom of exterior walls to get a good seal. Built in this fashion, your walls will ‘dry’ to the outside, reducing the need for dehumidifying inside.

Of course you will want to get approval from your local permit issuing jurisdiction before moving forward.

For extended reading on rock wool insulation please see https://www.hansenpolebuildings.com/2013/03/roxul-insulation/

Post Frame Barndominium Exterior Wall

Post Frame Barndominium Exterior Wall Questions

Reader IAN in RIDGWAY writes:

“I am looking for help understanding a couple of exterior wall questions.  

  1. My county is enforcing the 2018 IECC for energy efficiency. In my region this requires R-20 cavity + R-5 exterior wall assembly.  From everything I’ve read, this means a continuous layer of 1″ rigid between the framing members and the metal siding.  Is this an accurate understanding in your mind?  Does the 1″ of rigid between framing and siding affect the integrity of the structure at all?  Are the fasteners that are shipped with your kits long enough to accommodate the 1″?
  1. We will be living in our pole building, which means we will need to meet minimum code standards for receptacles at the exterior walls.  I am under the impression that the poles must remain whole and are not designed to have a hole drilled through each for ease of pulling wire.  Am I correct here?  What is the suggested solution? Conduit everywhere below my slab?”

Mike the Pole Barn Guru responds:


Nice to see jurisdictions enforcing IECC (International Energy Conservation Code) requirements, as it will result in more energy efficient structures. In Ouray County, you are in Climate Zone 6B. This requires ceiling R-49, wood frame walls of R-20 plus R-5 (or R-13 plus R-10) where second value is continuous insulation and slab edges to have R-10 four feet deep.

According to Martin Holladay (Green Building Advisor editor) your continuous insulation is just as effective when installed on the interior of your wall framing. This is very important when it comes to fully engineered post frame construction. Properly engineered, post frame construction relies upon shear strength of steel skin to transfer wind loads through building planes to ground (https://www.hansenpolebuildings.com/2011/12/lateral-wind-loads/). Having rigid insulation between framing and siding would reduce or negate your siding’s shear strength and result in a less than satisfactory outcome. My recommendation would be to use a Weather Resistant Barrier on the outside of the framing, directly inside of steel siding. Fill insulation cavity with unfaced batts (preferably stone wool such a Roxul as it is not affected by moisture https://www.hansenpolebuildings.com/2013/03/roxul-insulation/) or BIBs (https://www.hansenpolebuildings.com/2011/11/bibs/), then a well sealed rigid insulation board between framing and interior finish. Done this way, your wall will ‘dry’ to the exterior, making your home’s HVAC system less responsible for reducing interior humidity levels.

Your wire pulling is far easier than you may have initially envisioned. 

Very little drilling, if any, will be needed for holes in order to run electrical wires. Wall framing (girts) extend or are placed so as to leave a 1-1/2 inch space between outside of wall columns and siding.

Think of a hole being drilled through as being an “open knot”. Lumber grading rules refer to these as being “Unsound or Loose Knots and Holes” due to any cause. Most structural framing – like wall girts and roof purlins or posts and timbers are graded as Number 2.

For practical purposes, a hole up to just less than ¼ of board face being drilled through will be within grade in #2 lumber. Example: 3-1/2” face of a 2×4 a hole up to 7/8” may be drilled through, as often as every two feet. Allowable hole sizes are reduced and spacing increased for higher grades of lumber. 

Any holes drilled through pressure preservative treated lumber or columns, especially near         grade, should be treated with a Copper Naphthenate solution. Copper Naphthenate is available as a brush-on (Cuprinol No. 10 Copper-Green® Wood Preserver          https://www.homedepot.com/p/Copper-Green-1-gal-Wood-Preservative-176223/300502829)

or spray-on(https://www.homedepot.com/p/Copper-Green-Wood-Preservative-14-fl-oz-  

       Aerosol-CopperSpr/100191444)

Blower Door Testing Your New Barndominium Part II

Continued from yesterday’s blog;

Aside from code compliance or indoor air quality concerns, another reason to get a blower door test is to properly size your furnace or air conditioner. How leaky or tight your barndominium is can change how much heating/humidification or cooling/dehumidification you need. This then ties into how carefully your mechanical system is designed. If in doubt, ask your HVAC designer whether and how they use air leakage metrics in their load calculations.

Envelope leakage is measured in terms of air volume per time unit or CFM (cubic feet of air per minute). From this number, a standard metric called ACH50 (air changes per hour at a 50 pascal standard test pressure) is calculated. ACH50 indicates how many times building interior air volume changes with outside air under test conditions, correlating to air leakage under normal or “natural” conditions. This ACH50 number is how leakage across different homes is compared. CFM per floor area square foot and CFM per building envelope square foot may also be used.

Blower door testing is often done near the building process, when paint is done,  doors and windows are in place, and all weather stripping is installed.

This is a great time to find out your final numbers, but not such a great time to try and fix any issues. Doing leakage testing at different construction stages can help diagnose issues and fix them while the primary air barrier is still accessible. Caveat to this early testing is all window or door openings must be sealed, otherwise you won’t be able to pressurize the building enough to look for leaks.

To find someone to conduct blower door testing Google for a testing company using keywords such as: energy code testing, HERS Rater, or energy auditor. Ideally, you’ll find someone who is RESNET- or BPI-certified, meaning they should have right equipment and experience to help get a leakage number and also identify where leakage is coming from.

One can even make their own equipment with a box fan or two, and some ISO board to seal up the door opening. This will not get any actual leakage numbers, but it can go a long way in helping find leaks. When pulling air in through leaks by blowing air out of your barndominium, you can usually feel where air is coming in.  Depending on temperature difference, you might also be able to see it with an infrared (IR) camera. Another great tool to use is a theatrical fogger to help make air movement visible. 

Energy amount saved by air-sealing your barndominium depends on many factors: what climate zone you live in, interior temperature, wind speeds, etc. International Energy Conservation Code (IECC) required a 7 ACH50 building envelope leakage in 2009, but now 2018 code requires 3 and 5 ACH50 in most areas. This downward trend in leakage requirements indicates building codes will continue to get more stringent over time as builders get used to these standards, and as products and technologies improve. Achieving a 3-5 ACH50 is more than doable. These days, Passive House projects are required to achieve 0.6 ACH50. All of this is done to save energy on a large scale.