My post from yesterday got a lot of comments and questions leaving me obligated to write this follow up.
To reiterate, climate change is way too vast a topic for a single post, please be patient and follow the series.
Part 1 was Building Shell. For efficiency a building shell needs to be air tight and well insulated. How much insulation is needed to be considered well insulated? It depends! My #1 recommendation is HIRE A CONSULTANT!! It is way too easy for the average person with no technical background to get lost in the weeds. Three good places to start to find a consultant:
Passive House Institute USA. www.phius.org/...
A Knowledgeable local architect or engineer.
Building Science Corporation www.buildingscience.com
Having said that, let’s explore some of the questions/comments.
#1 Myth “A house needs to breathe.” aka “If my house is too tight, I will suffocate.”
The purpose of air sealing to to eliminate as much as possible uncontrolled air exchange with the outside. Infiltration of outside air is a major source of heat loss and air coming through the walls is often polluted with mold or formaldehyde.
Air exchange needs to be controlled. All high performance buildings have good ventilation built into the design. It requires a heat recovery or energy recovery ventilator. The outside air is warmed as it enters by the departing inside air resulting in way less heat loss and higher air quality.
#2 Question My house was built with the best insulation available, spray foam etc…. Why do I still have heating and cooling bills?
This question simply proves my point. If you still have heating costs or use more than minimal AC you don’t have the best insulation available. The typical builder knows next to nothing about insulation or efficiency. There is no good way to insulate without thickness. Resistance to heat flow is measured per inch. Thicker walls are better. How thick is thick enough? It depends on floor plan, climate, ratio of surface area to volume etc. If you are not an engineer, HIRE A CONSULTANT!! Basements and foundations are often the weak point. Insulation needs to be contiguous meaning the foundation insulation must extend all the way to the wall insulation which must extend all the way to ceiling or roof insulation. Trace a diagram of the insulation line with a pencil. If you lifted the pencil off the page at any point, you just found your weakness.
The least expensive most environmentally friendly way to have thick, energy efficient walls is known as an offset double stud wall. two parallel walls are built as far apart as you need the insulation to be thick. Studs are normally 16” on center. The walls a built with the studs offset 8” so the framing in one wall is dead center between 2 studs in the other wall, hence the name. The resulting cavity is blown in with cellulose insulation, which is made from recycled newspaper. This construction eliminates thermal bridging through the framing.
Thick walls tend to make windows and doors slightly “tunnel like.” This sort of freaks people out because it is outside the norm. Apparently, out of ignorance, they would rather fry the planet than have an abnormal house.
#3 Comment Poor people can’t afford this. Absolutely TRUE!
This is why the changes need be achieved through the building codes. (This supports my thesis that this is a political problem.) That way even a low cost developer or shady landlord trying to make a buck by saddling tenants with high utility costs is required to follow best practices.
#4 Comment Spray foam is highly damaging to the climate. True AND False
The propellants used for spray foam have historically been chemicals with extremely high GWP (Global Warming Potential). Some of them had GWP’s well over 1000 which means one molecule of the propellant is equivalent to over 1000 molecules of CO2. To make it worse, the chemical are stable and persist in the atmosphere. Some of the earliest spray foam installed will do more damage to the climate through their installation than all the CO2 emissions they will save over their life. Raw deal for mother earth.
The problem has been recognized and addressed, BUT be sure your contractor is using environmentally friendly technology before hiring. Some of the currently available foams use low GWP propellants as low as 1 or even water vapor.
#5 This is great for new construction, but what about the houses already here, especially the old one built in the late 1800’s and early 1900’s. We can’t afford to just abandon them. Excellent Question and GREAT POINT!
There is a process known as a deep energy saving retrofit. Its easy to get lost in the weeds on this one, but I will make a few comment here.
First and foremost, be sure you have modern wiring. It is Illegal to insulate of certain types of wiring. If your walls are hollow, blow them in with dense pack cellulose. Dense pack is not a type, but an installation technique. If your contractor does not know what dense pack means, find a different contractor!
Your walls are now somewhere around R 10-14.
The picture at the top is a Sears Four Square house of about the age in question that was retrofit by the principals of Building Science Corporation. They removed the old siding and used house wrap. Then they installed 4” of polyisocyanurate foam by using two layers of 2” insulation taping the seams and offsetting the seams between the two layers to reduce any air or heat flow. The insulation is held in place by furring strips screwed back to the original framing with 6” construction screws. The picture shows the house at the end of this step ready for siding. Polyiso is R 6. 4 inches is R 24. Now the wall assembly is in the ball park of 34-38; this is better than most new construction.
Basements get complicated, but they must be insulated. You can lay foam on the floor and pour a new floor. Yes you will lose ceiling height, would you rather fry the planet?. Walls can be done with board or spray foam inside or out, but inside is easier. For more information visit a web link above or, HIRE A CONSULTANT!!
#6 Smaller is better! Yes and No.
McMansions are a bad idea for more than just the earth. Studies have found that families living in smaller houses are more connected and happier than when they drift off into their own spaces.
But…
Larger buildings are more energy efficient due to the reduced ratio of surface area to volume. Tiny houses are horrendously inefficient due to their extremely high ratio of surface area to volume. They are cheap because they are small, but per square foot, they are energy hogs.
Now let’s imagine a bunch of tiny house pushed together. One tiny house’s east wall butts up against the next ones west wall. One houses floor sits atop another houses ceiling. You can’t lose heat to heated space. The houses keep each other warm. Voila, you have an apartment building. This is the most energy efficient way to live. Imagine living in a a high rise 12 story building surrounded by woods and gardens. By putting all the yards together and living in a tower you can have your own small but shared estate.
We need to radically reconsider housing, but all the technology we need already exists.
Part 2 will be powering the home.