Insulation is an important component for homes in that it reduces heat flow out of a house in winter and reduces heat flow in to the house during the summer. It is estimated that approximately 53% of energy consumed in a home is for heating and air conditioning.
Proper design and installation of insulation around the perimeter of the conditioned space (called the thermal boundary which separates areas that are heated and cooled from spaces that are not) can drastically reduce the energy required for heating and cooling homes and contribute to the comfort experienced by its occupants.
The keys to an effective wall are:
- Airtight construction—all air leaks in the wall assembly sealed during construction prior to insulation installation, continuous air barriers installed on both interior and exterior surfaces.
- Moisture control—exterior rain drainage system, vapor retarder located on the appropriate side of the wall.
- Complete insulation coverage—advanced framing to maximize insulation coverage and reduce thermal bridging, no gaps or compressed insulation, continuous insulated sheathing.
The full benefits of insulation can only be attained when it is installed properly. Gaps and compressed areas in the insulation can cut savings over 25%. Poor installation also leads to condensation and comfort problems.
(“Insulating a New Home: Do It Right the First Time”. Building Envelope Research; Insulation Fact Sheet. Accessed 1 April 2009.)
What Should Be Insulated?
- Attic spaces, including access doors to unfinished attics and knee walls
- Ducts in unconditioned spaces
- Exterior walls
- Foundations, including Basements, Crawl spaces, and Slab-on-grade floors
The ULTIMATE GOAL of insulating any home should always be to create a continuous thermal boundary. A properly sealed, moisture-protected, and well insulated envelope helps increase comfort, reduce noise, and save on energy costs.
Which Type of Insulation is Right for the Job?
|R-Value per Inch||Usage||Pros||Cons||Cost|
|Polystyrene, Polyisocyanurate||R-4 to R-7 per inch of thickness||Foundation walls; exterior walls; below slab; floor joists;||High insulating value per inch of thickness; can act as an air barrier when joints are sealed; offers continuous insulation||Potential moisture issues; sunlight damage; insect problems; burns quickly||CAN BE NO COST TO HFH AFFILIATES!|
|R-3.2 to R-3.8 per inch of thickness||Walls; ceilings; attic||Sustainable; recycled product; sound deadening;||Damp-spray done by professionals; Dry blown can lose its R-value over time due to settling in attics||$0.15 to $0.21 sq/ft not including professional installation cost|
|R-2.6 to R-4.2 per inch of thickness||Unfinished walls, floors, ceilings, attic||Width suited to standard stud spacing; volunteer friendly
||Must be installed with all 6 sides touching a surface to be truly effective; gaps and voids are common||Relatively low compared to other types of insulation; $0.27 to $0.34 cents/sq ft for R-19 (5 1/2")|
|R-3.4 to R-3.8 for Open cell and R-3.8 to R-6.4 for Closed cell||New wall cavities; unfinished attics;||Ideal for irregularly shaped areas and around obstruction; air-seals||Must be installed by a professional||$1.25 to $2.25 sq/ft but also saves costs on air barrier materials, like caulking and house wrap|
How Do I Know if the Insulation Installation is Adequate?
There are three different grades of insulation installation that are used by builders and third-party verifiers:
Grade I: requires that the insulation material uniformly fills each cavity side-to-side and top-to-bottom, without substantial gaps or voids around obstructions (such as blocking orbridging), and is split, installed, and/or fitted tightly around wiring and other services in the cavity.
Grade II: shall be used to describe an installation with moderate to frequent installation defects: gaps around wiring, electrical outlets, plumbing and other intrusions; rounded edges or “shoulders”; or incomplete fill amounting to 10% or more of the area with less than 70% of the intended thickness (i.e., 30% compressed); or gaps and spaces running clear through the insulation.
("2006 Mortgage Industry National Home Energy Rating Systems Standards". Accessed 12 August 2009.)