Embedded Scribd iPaper - Requires Javascript and Flash Player
Residential Insulation
Michael J. Currie GrotonLocal.org 10 October 2007
Why we insulate?
To slow the transfer of heat -Heat is the form of energy exchanged between objects of different temperatures!
Outline
     Building Envelope R-values Insulation Types Insulation Case Study Other insights
 Health Factors  Installation  Tax incentives
 Discussion
Building Envelope -- the “skin” of your structure
The building envelope consists of all the surfaces that separate the controlled space from the uncontrolled space.  Primary envelope is the exterior of your home  Secondary envelope is a controlled space that bisects an uncontrolled space
-- ductwork in attic, pipes in basement, refridgerator, hot water heater
 Thermal bridges are lossy pathways across the envelope
To maximize efficiency of the home, all envelopes must be properly insulated.
R-values
 Industry measurement of the resistivity to heat flow, inverse of thermal conductivity (U)
R = 1/U
 Higher R-values (more insulation) prevent heat flow
Material Outside Air Film Siding Wood Bevel 1/2” Plywood Sheathing Fiberglass Batt 1/2” Drywall Inside Air Film Total Wall R-value 0.2 0.8 0.6 11.0 0.5 0.7 13.8
R = R1 + R2 + R3 + …
Units: ft2 .°F.hr/BTU
R-values cont’d
1 "Heat = (THOT # TCOLD ) Area R
Factor R-value Energy Usage
Amount of energy you must supply per hour
Temp Difference Area
This is the basis for your insulation strategy!
Example - Your front door
1 "Heat = (THOT # TCOLD ) Area R 1 170 = 3.7 BTU/hr
(65 " 25)
!
21
(3’ x 7’)
Annual heat loss is equivalent to 5 gallons of fuel oil. (1 gallon fuel oil = 140,000 BTU)
!
!
Recommended R-values
38 49 38 25 11 to 22 30
Band Joist
38
19
10 11
Types of Insulation
R per inch 3.1 2.1 2.2 - 3.7
4-6.5
various
Source: DOE Insulation Factsheet
R-value caveats
 Insulation manufacturers measure R-values in a lab, not in the real world…
 “Center of Cavity” -- only insulation, no structure,WYSIWYG  Clear Wall -- wall w/ minimal studs  Whole Wall -- wall w/ windows, corners, etc.
For a 2x6 wall w/ R-19 batts and studs 24” o.c.
Center of Cavity 21.6 Clear Wall 16.4 Whole Wall 13.7
Source: Oak Ridge National Labs
2/3
Extreme Cold Air and Moisture degrade R-value performance of batt and loose fill insulation
Moisture -7.5% per 1% moisture Extreme Cold
Heating and cooling days
 Degree day captures the average temperature below the typical heating set-point of 65° F Example: 10° F average temperature gives 55 degree days  Heating Days
6000 degree days
 Cooling Days
500 degree days
1400 1200 1000 800 600 400 200 0 Jan -200 Mar May Jun Aug Oct Nov 2005 2006

In New England, heating dominates energy consumption
Residential Case Study
    Built: 1978 Living Space: 2400 sq ft. Perimeter: 156 ft. Energy Usage:
800 gallons fuel oil and 20 kWh per day-(100 million BTU during the heating season)

Construction:
2x4, R-11 batts R-19 in cathedral ceiling Single/Double Pane Windows No basement insulation
What are the available options?
Upgrading Windows
Type Single Pane Single Pane w/ storm Double Pane, low e Triple Pane R-value 1.0 2.0 3.0 4.0 BTU/year/ sq ft. 144000 72000 48000 36000 Case study savings $16.88 per window $5.63 per window
Payback time is 50 to 200+ years! - Very bad news
Assumes: Fuel Oil is $2.50
Insulating Basement
 8’ below ground level temperature is 50 - 55° F during the winter. The equivalent number of degrees days during the heating season is 1800. For 1300 square feet of floor (R-value = 1.6), the heating load is equivalent to 300 gallons of fuel oil ($750). The actual value is higher if the basement has drafts, i.e. the underground temperature is higher.  How to insulate?
 Do not use fiberglass if the area is moist. Your investment will be ruined.  Ceiling -- basement is unheated, attacks the problem at the source.  Walls -- basement is heated, fairly dry.  Always insulate band joist R30
External Foam under clapboarding
 Can you economically add foam over siding, if you intend to change siding?
Material Outside Air Film Siding Wood Bevel 1” Rigid Insulation Air Pocket Siding Wood Bevel 1/2” Plywood Sheathing Fiberglass Batt 1/2” Drywall Inside Air Film Total Wall Old Rvalue 0.2 0.8 0.6 11.0 0.5 0.7 13.8 New Rvalue 0.2 0.8 5 1.0 0.8 0.6 11.0 0.5 0.7 20.6
 Case Study: 1500 sq. ft. of siding -- savings of 53 gallons of fuel oil or $115 per year.  Not economical if you need to change any aspect of window detail, most likely over 10 year pay back time!
Case Study Conclusions
 Basement Insulation would be a sure bet. Large possible savings, with easy access on the inside.  Replacement windows and insulation under new clapboarding are not cost effective.  Other options:
 For windows: R-5 insert into windows at night would yield $5 per window per year.  Two other elements of the heat loss equation
 Reduce square footage -- only heat required rooms  Reduce setpoint -- 7 degree setback for overnight saves 11% across whole structure during the heating season
 Can be achieved with programmable thermostats
Other Factors
 Health Factors
 Vermiculite fill may contain asbestos
 70% of vermiculite mined from contaminated mine in Libby, MT
 Fiberglass insulation is a skin and airway irritant, and can contain carcinogens, formaldehyde allergens  Wet insulation supports mold growth
 Installation
 Improper installation may degrade whole wall r-value
 Fiberglass should not be compressed, voids behind junction boxes should be insulated, area around door/window frames
 Vapor barrier products must have vapor barrier facing high moisture area.
 Tax Incentives
 Energy Policy Act of 2005 -- credit of 10% up to $500 for the cost of qualifying energy efficiency purchases, i.e. insulation and appliances
Discussion