Current conventional insulation, fiberglass and cellulose, are readily available in rolls or blown forms. While, conventional insulation provides some form of resistance to heat transfer, its overall effectiveness needs significant improvement. Approximately 40 years ago, foam insulation was first introduced into the construction industry. The initial introduction was plagued with problems, off gas of formaldehyde and VOCs, material shrinkage, and sensitivity to off gassing chemical and VOCs. However, through years of improvements in research and development, raw material quality and installation equipment, the development of open cell and closed cell foam have significantly improve thus greatly improving the ability to insulate a home/building.
When addressing heat transfer into and out of a housing/building structure, one needs to address all three forms of heat transfer:
- Conduction – conduction is the transfer of heat through a solid member such as studs in your walls and roof, sheathings, etc… The resistance to conductive heat transfer (R-values) is the current standards used for by the industry to measure the effectiveness of the insulation.
- Convection – convection is the transfer of heat through a viscous material such as air. Regardless of the R-values, if the insulation material allows air to transfer/move through it, its overall insulation effective performance is significantly diminished. How effectively a structure have been built to resist convective heat transfer can be measured through the use of “blow door testing”
- Radiant – radiant heat transfer is the transfer of heat through energy waves. For example, the roof from a conventionally vented attic absorbs heat energy from the sun and heats up to temperature in excess of 160 degree F. The heat is then transferred through the roof sheathing and studs through conductive heat transfer and then re-radiate inward into the attic. The result is an attic with temperature in excess of 130 degree F or more. While reflective sheathings and reflective foil claims to reduce the heat by 17 to 30%, a foam insulated attic will stop up to 95% of total heat transfer into the attic.
Why is R-value not a true representative example of insulation values?
In a conventionally insulated home, conductive heat transfers only accounts for about 10-20% of the total heat lost and gains. Convective heat lost can accounts for as much as 60% of the total heat lost and heat gains. In addition, radiant heat transfer (heat gains from the sun’s radiant energy) will account for the remaining 20-30%. Furthermore, the R-values of conventional insulations are tested in a laboratory setting and does not take real life conditions into account. Studies have shown that fiber glass insulation installed where air transfer are allow to circulate through it, will performed only at 30-50% of the claimed insulation values (ie. An R 13 in the exterior walls is only as effective as an R-5 to R-7 in actual performance value.) It is this author’s opinion that the department of Insurance and Department of Energy reconsider the current and obsolete manor for determining the true insulated values of an insulation by taken into account not just resistance to conductive heat transfer (R-values), but also heat lost and gain through convective and radiant heat transfer. Oak Ridge National Laboratory (ORNL) conducted an experiment (*) to determine the efficiency of a roof assembly insulated with low density, loose-fill fiberglass insulation and discovered that up to 50% of the heat loss occurred as a result of convection; air circulation through the insulation. This result showed that the air-permeable insulation had loss its anticipated thermal performance level by half and that convective heat transfer had a significant negative impact on insulation performance.
Closed Cell (Medium Density) Foam vs Open Cell (Low Density) Foam.
There currently exist two types of foam being use in residential applications: Open cell – Low density foam, and Closed Cell – Medium density foam. There are positive and negative to both products:
Open Cell Positives:
- High thermal efficiency, performed at 98% of prescriptive R-values
- Lower cost – approximately 50% the cost of closed cell foam for same prescriptive R-values
- Same thermal efficiency as closed cell at half the cost
- Is a registered air barrier at 3.5” for most open cell foam
- Cured in under 1 minute
- Has zero off-gas
- Does not create dust
- When engineered with the HVAC system: provides for a healthy, energy efficient, low humidity, and comfortable indoor air quality
- Adds toward building structure strength
- Is a durable building material – certain manufactures will guarantee the product for the life of the structure
- Excellent at suppressing audible noise
- Has low environmental effects
Open Cell Negative:
- Is not a vapor barrier, so in northern climate zones a vapor barrier (6 mil plastic) is required on the inside of the thermal envelope
- Some open cell foam product will wick water, if this trait is high in a foam product, it could lead to water issues if house is not properly dried in (seek out hydrophobic foam products)
- Requires significant trimming and has large quantity of waste
Closed Cell Positive:
- Higher R-values per inch when compared to conventional insulation and open cell foam.
- Is a vapor barrier
- Provide significant strength to building
- Excellent at suppressing audible noise
- Is a durable building material – certain manufactures will guarantee the product for the life of the structure
- Does not create dust
- Is a vapor and air barrier
Closed Cell Negative:
- Extensive period of off-gas (up to 2 years)
- Not recommended for people with sensitivity to chemicals, allergy, or have respiratory issues
- VOCs
- In North Carolina, the vapor barrier is placed on the wrong side of the building
- Closed cell foam underneath roof can result in roof rot is roof leaks occur
- Experienced company like Healthy Home Insulation, LLC who installed both open and closed cell foam has made it a practice to not utilized closed cell foam in residential application due to the health water damage liabilities.
Conclusion:
As a consumer, we can significant reduce utility cost for heating and cooling our new and existing homes by 50-70%. We can live in a home with superior indoor air quality, is quiet and comfortable. Foam insulation is the most energy efficient insulation product currently available in the market. The use of foam insulation should however, must be incorporated into the house as a system and not use just as a single building product. Correct sizing of the HVAC system(s) by an experience HVAC contractor or building engineer is strongly recommended and will provide for maximum energy efficiency, long-Gevity of the HVAC equipment, proper ventilation and dehumidification of indoor air quality, comfort and a healthy indoor air conditions. Foam insulation is one of the very few building product that can provide an immediate return on investment for new construction and has a ROI in existing retrofit projects in as little as two years.
Written by: Tu N. Nguyen, Healthy Home Insulation LLC.
Parade of Homes Gold Winner 2009, 2010, 2011, 2015, 2016, 2017, 2022 & 2023
