In our last post we looked at how we reinvented our framing for the next generation of home building. Our owners get 4 times the insulation of a “green home” all while reducing waste and greatly improving daily living and durability. In this post we will look at the next steps for this structure; the weather sealing and insulation. Now we’ve already talked in past posts about how all the parts of our homes function as one integrated system. There probably isn’t any better example of this than the relation between framing, insulation and weather sealing. Let’s take a look at the top things we are doing differently.
1 | don’t forget to breathe
Sounds obvious right? People can’t live without breathing and neither can any other living organism. Buildings aren’t any different. As buildings become more air tight and energy efficient (and what new home isn’t marketed as energy efficient) breathing properly becomes increasingly more important. Unfortunately the easy and common ways of building more air tight and energy efficient force a home to essentially hold its breath! Add unvented stucco to the outside (nearly all stucco in Arizona) and you have yourself a perfect petri dish for growing mold.
During winter months physics forces moisture from inside a home through walls and to the outside. During summer this reverses with the AC pulling moisture inside. In a mixed climate like Arizona it is critical for a home to breathe in both directions. We use a 4 part system called R-Guard to fully air seal every home (more about how tight later) while also letting any trapped moisture move freely into our vented siding system and away. This is a little trick we borrowed from pretty much every tree in history.
Now that the house is sealed so tight we install a lung of sorts (called an HRV) that constantly pulls out “bad” air from bathrooms and kitchens and delivers pre-conditioned and pre-filtered fresh air to living and sleeping spaces. All at the perfect and controlled rate, exchanging all air in the house once every 3 hours.
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2 | sun and rain are our friends
It’s no secret that Arizona has a lot of sun….and a many of us who live here like that fact. There’s also no time quite as magical in the desert than the hours and days after a big rain. The desert literally comes to life.
The Sonoran desert may often be dry but it’s actually a very challenging climate for controlling moisture within buildings. Summer monsoons are particularly challenging with the combination of large amounts of water, heat and sun on the outside driving moisture into a home’s walls all while the comfy AC is pulling moisture in from the inside.
Old brick homes let this moisture breath in all directions. Not the best idea but also not a ticking time bomb. These homes are continually uncomfortable and can offer ideal habitats for termites and other pests but you generally know what you’re getting.
Poorly designed “energy efficient” homes do a lousy job of keeping the moisture out to begin with and then trap it inside the walls after getting past the first line of exterior defense. This trapped moisture nearly guarantees very bad things to happen, it’s just a matter of time.
Vali homes use our interpretation of a vented rainscreen that we call a “heatscreen” to create a pressure difference between the actual siding and sealed wall structure. This area of low pressure lets moisture accumulate and drain down our R-Guard barrier before it can get into a home’s wall. The R-Guard barrier itself is also water proof and self sealing around any fasteners so there’s no pesky tiny cracks for moisture to seep through. You would be amazed at how small of a crack within a typical system can create devastating damage.
3 | insulation makes a bad air filter
Typical walls have random gaps all over a home. Without constant, balanced air exchange like an HRV pressure differences pull and push air through these cracks. Even worse typical homes rely on bath fans to pull “bad” air out of a house, create negative pressure and suck “fresh” air through these random cracks. All of this air comes inside a home with no filtration and no conditioning. That means during a 110 degree dust storm you have 110 degree dusty air flying into your home.
In contrast Vali homes are perfectly sealed allowing insulation to act like insulation and air filters to filter controlled, incoming fresh air. This also makes walls and insulation last much longer. There is very little to make the insulation deteriorate and lose effectiveness. It will function just as well in 60 years as on day 1.
4 | how tight
The best way to calculate how well a home has been air sealed is through a blower door test. This is so important I would say never buy a home without seeing the results. This test depressurizes a home and then measures the amount of air leaving at that given pressure, measured in CFM. The easiest way to understand the results is in the cumulative hole size.
Before we knew about energy efficiency (think 1950’s brick homes) typical homes had countless holes and cracks. Think a cumulative hole size of a jumbo beach ball (Basically equivalent to driving around with your car windows halfway down all the time. On hot or cold days these homes can leak out all the conditioned air as quickly as once an hour.). On moderate days where outside and inside temps are similar it may take even the leakiest buildings 8+ hours to exchange all the stale inside air with fresh outside air. This leads to wasted money half the year and bad air quality the whole year.
Then the building industry spent a generation building progressively more air tight and efficient homes. Unfortunately this was more of a “plug up the holes in the sinking boat” approach rather than a “build a better boat” approach. Through this mission the industry got that cumulative hole size down to about a basketball. Through this time period we started to realize sick building syndrome. Buildings were literally killing the people living and working inside them, sometimes slowly, sometimes alarmingly quickly.
Fortunately lots of really smart and scientific people have already developed and thoroughly tested better ways. Most important is looking at the house as a complete system. With this new technology and testing tools we can build homes nearly perfectly air tight while still allowing them to breath moisture naturally (like a tree) to prevent mold growth and other issues. In fact we recently doubled the Arizona record with a blower test of 0.3ACH50Pa which is a cumulative hole size smaller than a golf ball in a 1,680sf house all while letting moisture breathe freely!
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5 | don’t forget about the inside
Most insulated spaces are air sealed on only one side. In many climates that is often non-breathing plastic on the inside (generally a bad idea). In hot or mixed climates the easiest way is to spray foam the exterior sheathing, from the inside. Neither of these are a good option and both slow or stop moisture from moving out of a wall.
After totally sealing our homes from the outside with the breathable material the inside is somewhat of a bonus. During winter months moisture wants to move from inside a house into the walls and the walls to the outside. During Summer while running the AC the opposite happens. Keeping the framing and insulation as dry as possible is the goal. For this reason we use a very special material called Intello+. This functions as a full interior air barrier all year but changes moisture permeability with the seasons. During the winter the Intello keeps moisture from moving into the walls while they dry to the outside. During the summer any moisture that somehow gets in the walls can move freely to the inside.
6 | air doesn’t insulate
Batt insulation is still common for a reason, they are cheap. Insulation comes out in big rolls, gets cut to size and quickly stapled to the wall framing. The downside is walls aren’t empty. They are full of wiring, piping and other utilities. This means that even a skilled installer of batt insulation will leave lots of little air pockets that function as uninsulated energy highways. This can easily cut the insulating effectiveness of a wall by 10-20% overall and 100% in the area with poor insulation. Think about a 1’x1′ spot of missing insulation directly next to your bed, that can make sleeping much more uncomfortable.
As an alternative we use dense packed cellulose. This process blows shredded insulation into the sealed wall cavity packing every crack and cranny with maximum insulation.
7 | don’t use foam
You may be thinking that foam insulation has many of the benefits above, and you would be mostly correct. We won’t get into the environmental issues of foam or the fact the installer has to wear a protective suit, you can make your own personal judgements on these points. The larger issue is 2 things; (1) Foam slows moisture transfer and keeps walls wet (2) foam attempts to be everything to everyone. By acting as an air sealing layer and insulation, spray foam doesn’t do either all that well on day 1 and gets worse as time goes.
By contrast our walls have already solved the moisture transfer and air sealing issues in other, more durable, higher performance ways. Now our insulation only has to insulate. That lets us use blown in cellulose which really is a miracle material of sorts. It’s 100% post consumer recycled, treated to be highly fire and bug resistant in a way safe to humans, insulates the smallest air spaces, absorbs and buffers moisture, resists mold grown, adds great sound proofing and is totally safe to install.
As always if you would like more info please head to our contact page. Don’t forget to ask the critical questions of your building professionals and never settle for the marketing jargon that doesn’t sit right with YOU.