Alternative Living, Design, DIY, Energy, Green Building, Small Housing

Energy Efficient House Framing

My little garage suite design project is in full swing, having recently laid out the interior floor plan and calculated how much insulation it would need in cold northern Calgary, Alberta, Canada.

The first step was to frame the walls and roof in SketchUp. Here’s what I have so far, having just messed around with adding insulation in between the wall studs and roof joists. I also just added the porch out front…clearly still lots to do!

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Before starting, framing in the grand scheme of house design seemed like a non-issue: stick a bunch of 2×4’s up, make room for doors and windows and ‘bam!’ you have a framed house. But it wasn’t long before discovering that framing, especially the roof and corners, was actually a big learning curve and slightly overwhelming. Not to mention, my goal was to make this thing energy efficient so I had to make wide walls and fancy intersections to accommodate thick bats of insulation and minimize the amount of wood used.

I poured through website after website searching for some good framing-for-dummies material and pictures, finding a surprising lack of basic information. Luckily, my trusty friend the public library had some great books on framing basics. Looks like the the internet lost this round!

The single best piece of advice I found was: ‘don’t try and frame the house as a whole, break it down in to manageable pieces. For example, frame the four walls independently. Building one wall, then another one, and then join them together.’ This sounds like common sense but mentally it made it infinitely less complicated.

FRAMING BASICS

Standard framing uses 2″x4″ boards (which are actually 1.5″ x 3.5″…a bit misleading) called ‘studs’, typically 8 feet long arranged 16 inches apart ‘on center’ to make up a wall. The roof is usually built with trusses that can be pre-made by a truss construction company. Framing a single wall is straight-forward enough, the tricky part is connecting them together when they meet, and also learning the hefty list of new vocabulary such as the ‘king stud’ and ‘top plate’:

wallframingPicture from here

STEEL FRAMING

The not-so-common cousin in the framing world is to use light-gauge steel as a substitute for wood lumber. It’s much lighter and usually has pre-drilled holes for electrical and ducts. Plus they are typically made with some recycled material, and can be recycled at the end-of-life. However, steel studs are only really useful in interior walls, as steel is a great heat conductor and would be a sieve for heat to escape.

ADVANCED FRAMING

Advanced framing, which seems like an odd name as it sounds complicated and intricate, should just be called ‘modified framing’ or something, as it simply uses a few clever techniques to reduce the amount of wood needed and create thicker walls. The main difference is the use of 2″x6″ wood studs, and everything is purposefully stacked to have all loads on top of one another. This way, there’s no redundant load-bearing supports needed, saving considerable wood and cost.

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On the left is an image from Green Building Advisor, where you can clearly see how everything is nicely stacked from ground floor to roof, and minimal extra framing is added around the door and windows.

ENGINEERED PRODUCTS

Several clever engineered structural materials exist, which are stronger, span further distances, look super cool, and reduce raw lumber required. And with any engineered product, it can’t just have a simple name, it has to be an abbreviation.

Here’s a few:

SIP (Structurally Insulated Panel) – it’s like an ice cream sandwich, but with insulation as the tasty center, squished in between two pieces of OSB (oriented strand board). There’s numerous companies that make them.

3301506_origPicture from here

LVL (Laminated Veneer Lumber) – these are made by gluing thin strips of wood together with adhesives to make strong beams for headers and joists. If you go in any unfinished basement you’ll likely see one spanning the middle of the ceiling. A great product but keep in mind those adhesives can contain volatile compounds and might not be great for your health.

TJI Joist – I can’t figure out if TJI actually stands for anything…regardless, this is a joist that can be used to make floors or roofs. They’re usually called an I-Joist for how its cross section looks like the letter ‘I.” (not shown in this font, but you know what I mean) They’re exceptionally strong for their weight, can span large distances and don’t bow or twist like regular lumber can. Here’s some TJI I-joists, ending at a LVL beam:

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Picture from here

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