Reducing the need for air conditioning

Grape arbor sun protectionHow long have we been building houses?  A lot longer than we have been air conditioning houses.

Well we have certainly done things to keep warmer and dryer for thousands if not 100’s of thousands of years–but we have also done things to keep them cooler as well.

As a designer/builder for most of my adult working life, I have marveled at how ignorant we are of how to accomplish keeping warm, dry and cool.

We now have air conditioning systems that allow us to live in places where not too long ago it would have been considered uninhabitable–or at least inhospitable.

We have long had the knowledge to mitigate the use of air conditioning to some degree and yet we simply choose to turn down the knob on the thermostat.

Today I just want to talk about a few “passive” things that can be done to greatly decrease the use of actual mechanical air conditioners.

First and most important is house design and orientation. Obviously if we build a house and make all the south facing walls floor-to-ceiling glass, with no roof overhangs, we can expect to find ourselves inside a solar heated oven. Just providing a roof overhang to prevent the sun from hitting the windows directly can go a long way to turn the oven down a bit. By eliminating ground and other surfaces that might reflect the sun’s rays into the home can also be an improvement.

Even these Native Americans made an attempt at basic principles

Of course reducing the amount of glass itself will make the most difference because then the walls themselves can be better insulated. This brings us to the huge topic of insulation in general. There is nothing like highly effective insulation in the walls and ceilings to keep the heat out of the house. This is not as simple as it may seem because heat is always attempting to move to cold and make balance. When it is 95 degrees outside, all that hot air is just hungry to gobble up our pathetic little bubble of coolness. So our air conditioners have to work their butts off to maintain that bubble of coolness.

While today I do not want to go into how I think houses should be built to eliminate the need for air conditioners altogether in many areas, I want to talk about ways we can deal with adverse conditions in our older homes in passive ways. While these things will not reduce your need for air conditioning in some areas it may greatly reduce the amount they may have to run. It may mean in some hot humid areas you might have to add a dehumidifier to make up for what the AC used to do.

The short story in all of this is to insulate your house as much as practical and use good air sealing type insulation–anything longer and we are into the full fledged novel.

One of the most important things you can do, if you live in an area where the nighttime temperature drops even 20 degrees between daytime and nighttime, is to change the air in the home and lower the thermal loading that has built up in the home during the day. The house is then closed up during the day to keep the nighttime cooling in and then the process simply repeats itself. In an average size house, even a simple window fan in a window on one side of the house and a window open on the opposite side of the house can accomplish this goal.

I cannot stress the importance of roof overhangs to keep the sun out, but in older homes that is not likely going to be possible.

In my own house, built in the early 30’s, the overhangs are insufficient to keep the south facing windows from overheating the house in the summer. So a simple thing I have done is to shade the windows with a grape arbor–the one plant now creates shading of most of my south facing windows and makes an amazing difference, and of course provides grapes in the fall.

Grape arbor sun protection

While we certainly do not get as hot as lots of areas of the country, my house certainly never needs any mechanical air conditioning. The attic has a ton of cellulose fiber insulation, the walls have minimal insulation limited by the 2×4 wall thickness, and we put a fan in an east window at night and open up a west window–on those occasional really hot days.

Before the days of the grape arbor, we use to have to do the fan approach a lot more.

If you have a house with a basement, you can open up a basement window (as the path to the upper fan in the window) and get the benefit of the cooler basement to improve the cooling of the interior space during the nighttime. Accessing the constant ground temperature is another thing that can have a huge impact on minimizing the mechanical cooling needs of the home.

A huge number of homes across America could benefit from this passive approach to improving house comfort and energy efficiency.

By Charles Buell, Real Estate Inspections in Seattle

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What is a little missing insulation between friends?

Sometimes it is the little things that get you.

However, these little things can end up costing you a lot of money over time.

At a recent inspection I had a house where the insulation details were not well thought out.  Without going into a discussion about the “type” of insulation, lets just discuss in the simplest of terms how the system was working—or not working as the case might be. 

The following sketch shows how the walls are insulated up to the ceiling and then the roof plane itself is insulated.  What got missed was the wall between the roof and the ceiling.  This space above the ceiling is essentially “conditioned” space and the short wall between has to be insulated to have continuous insulation around the conditioned space.

This next picture shows what that un-insulated area looks like with thermal imaging from the exterior.  However this is a space between the second floor and the main floor ceiling.

Going back to the original drawing, here is an exterior view of that un-insulated space—as seen by thermal imaging.  The un-insulated areas appear warmer (the white-yellow areas)

The same areas of the above picture as seen from the inside of the attic space with the un-insulated areas appearing “cooler” (the black areas).

These areas will need to be well-insulated to prevent wasting of energy that increases both heating and cooling loads of the home. 

The fiberglass insulation should be encapsulated, and for more information about that:  All Fiberglass Insulation Must be Encapsulated.

 By Charles Buell, Real Estate Inspections in Seattle

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All fiberglass insulation must be encapsulated!

I suspect this will rub up against common wisdom and even standard building practices, but it is an idea that’s time has come.

Un-encapsulated insulation is at its best a good filter, as is demonstrated over and over with the dust that shows up from air moving through it. It is not surprisingly–used in filters–like furnace filters.  That same insulation “quantity” becomes much more effective when it is enclosed on both sides.  In this first picture we can see black sooting of the insulation where air is leaking around an ICAT type can-light buried in 16 inches of white fluffy fiberglass insulation.


Fiberglass insulation, without an air barrier on both sides, is very poor at stopping air moving through the insulation and into the attic around can  lights, junction boxes, exhaust fan housings etc.  Of course these penetrations should be properly air sealed regardless, but when there are breaches, the fiberglass cannot help, as can be seen in the next two pictures.

Hall (210)Hall (211)

The R-value of any insulation is only as good as its ability to stop air movement. Fiberglass insulation is very poor at stopping this air movement. Loose fill cellulose fiber, spray cellulose fiber, foam boards and the spray foams are much better at this.

So one might ask, well that is fine for side walls, but what about attics and crawl spaces? The answer is simple–don’t use fiberglass in those installations. Pick an insulation that is better at stopping air movement or figure out a way to encapsulate the insulation.

This would not be impossible for crawl spaces, but quite difficult for attics without special framing changes or truss design changes etc. It is much easier to simply properly air seal the ceiling and then insulate with cellulose fiber or spray foam.

We should never see exposed batt type insulation in the transition walls between different levels of a home visible in the attic.

Colburn-full (298)Jorg 229

We should never see exposed batt type insulation around skylight chases.

Copy of Snell 325

We should never see exposed batt type insulation in the walls of knee-wall attics or the walls between crawl spaces and conditioned spaces, such as the next picture.

Colburn-full (310)

We should never see exposed batt type insulation on ductwork.

Gray 253

I am pretty sure it is time for the building codes to recognize this serious defect regarding the use of fiberglass with no encapsulation, and require that no fiberglass insulation ever be visible–that a proper continuous air barrier be installed on both sides.

Another requirement, related to good air sealing, would be that all drywall be continuous bead glued to at least top plates and bottom plates.  We can discuss that another time.

PS, if you are thinking of fixing your own ineffective fiberglass installation, all I can say is don’t.  It is not simple to do and things could co horribly wrong.  For example you generally would not want to just add plastic sheets to the underside of your floor joists to “encapsulate” your insulation.  This would be  a very bad idea in most climates if the plastic is a vapor barrier.  Consult with a qualified Building Performance Professional before making any changes to the way your house is insulated.


By Charles Buell, Real Estate Inspections in Seattle

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