Superinsulating the Attic: An easy way to improve home energy efficiency

One of the easiest ways to dramatically improve energy efficiency in an older home is to insulate the attic.  It’s a job that takes an insulation professional only a couple of hours to do, and besides the benefit of saving energy over time, it immediately makes the home more comfortable.  And quiet!!

Inches and R Value

Inches & R

Since heat rises, attic insulation is far more important than wall insulation.  Typically, most houses in American today have 3 to 6 inches of insulation in the attic.  This translates to an insulation value of about R-10 to R-15.  Adding enough insulation to make the attic “superinsulated” (14 inches of insulation for R-38 value, to 22 inches of insulation for R-60 value) typically costs around $1 per square foot.  Our recent project of adding R-30 cost less than $1000, and for this investment we expect a payback in 2 to 3 years.  We chose to finance the project through our account with the gas utility, so that if we were to move the next residents would take over the payments on the investment along with being able to reap the energy savings benefits.  According to an Energy Star study, the typical American house could use as much as 20% less energy for heating and cooling after some relatively inexpensive and easy improvements.  This typically means a 10% reduction in total house energy use.  These improvements include sealing common types of air leaks around the house as well as adding R-23 of attic insulation and insulating the floor over crawl spaces.

R10 Attic Insulation

Spraying fiberglass into an attic which had less than 4 inches of insulation (approx R-10)

Above and below are the BEFORE and AFTER shots of our recent attic insulation project.  We hired the job out, and were very glad we did!  The professionals have access to better equipment and have the experience to be able to spread the insulation around evenly.  The new fiberglass matterial feels like synthetic cotton balls.

Superinsulated Attic

An attic newly superinsulated with fiberglass insulation (R-40+)

Our recent project included adding ventilation baffles to ensure good air flow in the attic.  The final step was sealing and insulating the attic access hatch.  Our attic hatch is a square peice of sheet rock.  It was sealed by putting a rubber weather-strip around the perimeter.  For insulation, the access hatch was just surrounded by strips of insulation batts, and then one batt laid across the top.

We have been appreciating the quiet and comfort of having a superinsulated attic.  Now we wish we had done this sooner!

Step 1: The Home Energy Audit

It seemed logical to officially start the “Green My Bungalow” retrofit project by doing an energy audit on the house.  The idea was to have some baseline data on the current energy use of the house as a starting point, and see what recommendations the auditors might make.  A grant-funded non-profit organization called SustainableWorks is currently offering CityLight-subsidized home energy audits for the bargain price of $95.  Normally closer to $600, the audit was a thorough inspection of the energy use of the house, from attic to basement and everything in between.  The most exciting part, of course, was the blower door test, in which a large fan is placed in an exterior door to draw air out of the house.

Energy Audit

Blower Door Test for Energy Audit

The blower door test is like having all the bathroon fans, the kitchen fan, and the dryer on all at once, sucking the air out of the house, creating negative air pressure inside the house. As a result, outside air comes into the house through tiny and not-so-tiny leaks in the exterior walls, doors, and windows.  A special infra-red camera sees the temperature differential where the outside air is entering the house.    The energy audit took the inspectors several hours, and they concluded with a 16-page report.  Overall the house was rated as using slighly less energy than the average house for the area.  The report included ideas big and small for improving energy efficiency in the house.