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Fiberglass vs Spray Foam Deep Dive.
A question that often comes up when deciding what insulation to use is whether to use traditional fiberglass insulation or this new spray foam you’ve heard about.
Cost is one major factor in deciding what to use, but not the only one.
One question that often comes up when deciding what insulation to use is whether to use traditional fiberglass insulation or this new spray foam you’ve heard about. Cost is one major factor in deciding what to use, but not the only one.
Closed cell foam, which is used in our climate zone, is both an air barrier and a vapor retarder. Because it goes on as a liquid and expands in place, it gives great performance around piping, duct work, and odd shaped places of construction. This provides superior air sealing compared to fibrous materials even when they are covered with polyurethane.
When using fiber for insulation there are air flow patterns that can cause problems. One of these is looping within a stud cavity. Even when the face of the fiberglass has plastic over it to restrict air flow, it still moves within the material itself. The air that is on the cold side of the cavity cools and settles to the bottom while the air on the hot side of the cavity expands and rises to the top. This continual air exchange inside the cavity creates an inefficiency that can be stopped with foam. Because it is an air barrier there is no air exchange within the material. This means the air on the hot side stays on the hot side and the air on the cold side stays on the cold side.
Another pattern is air flow through the material. The traditional solution for this is to put polyurethane over the studs to stop airflow. In western Montana, since our vapor flow is inside to outside for most of the year, we put it on the inside to keep the vapor from flowing through the insulation. While this helps with airflow, it doesn’t stop it as there are holes cut for outlets, switches and pipes. However many people chose not to use polyurethane for one reason or another and these homes are left with no protection from air intrusion. Siding, osb, and drywall are not designed to stop air flow and they generally only reduce it. The inside of our homes being warmer than the outside for most of the year causes a lot of thermal pressure on the ceilings of our homes along with a vacuum on the lower walls and crawl space area. This can result in a large amount of airflow particularly on taller homes as the whole house acts as a chimney. When the crawl space is vented, this allows an easy route for air into the house, bringing with it any mold or moisture that has accumulated, and with all the lights and fixtures on the ceiling it has an easy exit right into the attic as well. A full solution to this is to spray foam the entire envelope of the house, but there are partial solutions that can help substantially as well.
One common practice in our area is to encapsulate the crawl space. This involves putting down a 6mil black plastic vapor barrier on the ground and then spraying foam from the top of the rim joist down to the edge of the plastic. This seals the crawl space from water intrusion, reducing or eliminating mold, as well as air, bugs, and dirt.
With this approach the crawl space now becomes part of the conditioned space of the house which keeps your floor feeling warmer, your water lines from freezing, as well as creating a barrier from any harmful gasses in the soil such as radon. It also keeps the cold air out and the warm air in to reduce your heating bill. As this is now conditioned space you will either want to open an air vent from the central air system into the crawl space or install a small fan on a humidistat that vents to the outside to control humidity levels in the area.
On new construction we often foam the walls as well to continue this seal up to the attic area. This usually costs no more than installing a flash and batt (1” of foam with a fiberglass batt over top) system and eliminates problems with condensation down the road.
This system drastically reduces airflow through the home by sealing up the lower portions of the house where the cold air tends to enter keeping better air quality inside.
While spray foam costs substantially more up front it often pays for itself in approximately 5 years when compared to a full fiberglass system because of increased efficiency which lower your energy costs.
Studies often show foam to be around twice as efficient as fiberglass when it comes to keeping you comfortable. Spray polyurethane foam (SPF) and fiberglass insulation are two popular options for insulating buildings. While both have their advantages and applications, SPF is often considered superior in several aspects.
Here are some reasons why SPF is often preferred over fiberglass insulation: Spray polyurethane foam (SPF) and fiberglass insulation are two popular options for insulating buildings. While both have their advantages and applications, SPF is often considered superior in several aspects. Here are some reasons why SPF is often preferred over fiberglass insulation.
Benefits of Spray Foam over Fiberglass Deep Dive.
Spray polyurethane foam (SPF) and fiberglass insulation are two popular options for insulating buildings. While both have their advantages and applications, SPF is often considered superior in several aspects. Here are some reasons why SPF is often preferred over fiberglass insulation:
Superior insulating properties: SPF has a higher R-value per inch compared to fiberglass insulation. R-value is a measure of thermal resistance, and a higher R-value indicates better insulation. SPF can provide a higher level of insulation with less material thickness, allowing for more efficient use of space.
Air sealing capabilities: SPF acts as an excellent air barrier, sealing gaps, cracks, and voids in the building envelope. It expands and fills in hard-to-reach areas, creating a continuous insulation layer that prevents air infiltration and reduces energy loss. Fiberglass insulation, on the other hand, can leave gaps and allow air leakage if not properly installed and sealed.
Moisture resistance: SPF is resistant to moisture and can help prevent water infiltration and condensation within the building. It can form a seamless, monolithic barrier that reduces the risk of mold growth and protects against moisture-related issues. Fiberglass insulation, if not properly installed or if it gets wet, can lose its insulating properties and may promote mold growth.
Improved sound insulation: SPF has good sound-dampening properties, reducing noise transmission through walls and floors. It can effectively minimize sound transfer and create a quieter indoor environment compared to fiberglass insulation.
Versatility and application: SPF can be applied in various forms, including open-cell and closed-cell foam, allowing for greater versatility in insulation projects. It can conform to irregular surfaces, filling cavities completely, and adhering to different materials. Fiberglass insulation comes in pre-cut batts or rolls, limiting its application to standard-sized spaces and requiring careful installation to avoid gaps.
One downside to SPF is that is costs significantly more upfront than fiberglass. These costs can be recouped over time through energy savings and in this regard it can be helpful to think of SPF as an investment. A typical house going from fiberglass to SPF often makes up the difference of cost in as little as 5 years. Any savings beyond the breakeven point is money in your pocket, for as long as you live in your home.
It’s worth noting that both SPF and fiberglass insulation have their specific uses and advantages depending on the requirements of the project. Factors such as budget, climate, building design, and personal preferences should be considered when choosing the appropriate insulation material. Consulting with a professional insulation contractor can provide further guidance based on your specific needs.
