Efficient Insulation for Marin County Homes: A Complete Overview

Apr 14, 2023General Contracting, Home Maintenance, Insulation, Remodeling




Spray Foam


Blow in Blanket


Rigid Board


Mineral Wool



The above list is in no particular order of preference. There are a number of different types of insulation, and even more ways insulation is used in a building or home. The “best” type of insulation depends on the situation. Simply put, there is no “best” type of insulation. However, there are reasonable best choices based on common existing scenarios. Some types are better used in new construction or unfinished spaces, others are easier to use for people interested in doing DIY home remodeling projects themselves. Some are inexpensive and easily installed, other types of insulation are costly to install and require experts in the field. Consider the following when selecting the best insulation for homes in Marin County or the San Francisco Bay Area.

What Does R Value Mean for Insulation?

If you don’t know already,  R-Value is a measure of how well a two dimensional barrier, such as a layer of insulation, a window or a complete wall or ceiling assembly, resists conductive flow of heat. The higher the R-value, the more resistance and the better the material is at insulating a building. Generally, insulation materials with higher R-values cost more when compared to those with lower R-values. R-values for insulation typically range anywhere from R10 for some flooring materials to R60 for dense attic insulation materials. R-value for other building materials (e.g., lumber, plywood) are generally considerably less that insulation. The assigned insulation R-value represents how much heat resistance the material has per inch of depth. That means a lower R-value material could provide a comparable amount of insulate properties as a higher R-value material. This would only be true if a greater depth is used. For example, one inch of insulation with an R-value of R60 is equal to two inches of insulation with an R-value of R30.


One of the top choices for many homeowners and general contractors in Sonoma County is fiberglass. It offers cost-effective insulation that maintains its shape over time and provides acoustic dampening. Fiberglass insulation is also fairly easy to install in a variety of spaces, and insulation subcontractors are very familiar working with this material. It comes in batt form or as a loose-fill material, and offers a high R-value or (thermal insulation). Types of fiberglass insulation include: encapsulated, batts, foil faced, un-faced and blown-in. Another large benefit to using Fiberglass is that it tends to keep its structure and resists moisture and mold to help preserve your home’s walls.

Potential downsides include the carbon footprint of creating the spun fibers, inhalation and skin irritations from the glass fibers, and it can “sag” in vertical wall assemblies leaving a cold patch at the top of a stud bay. Most fiberglass insulation used to contain added formaldehyde which would take years to off gas, but most available now in the US does not contain added formaldehyde.


Blown-in insulation is a method of installing insulation. A machine blows an insulation material such as fiberglass, or cellulose into the space, typically in attics. This type of application may rely on materials such as fiberglass, rock wool, or reclaimed cellulose material. Many times recycled newspapers or even cardboard is used. The benefit using this type of insulation application is that it conforms to fit nearly any type of location and base material. Blow-in insulation fits in the toughest of locations. In regard to blown-in insulation, R-values range from R-2.2 for fiberglass up to R-3.8 for dense cellulose. In summary, blown- in insulation is best used for adding insulation to horizontal areas or oddly shaped and hard to get spots. This method distribute’s insulation everywhere and in the process many fine particulates will be aerosolized. Use caution to protect your eyes and skin.

Simple insulation jobs may be possible to do it yourself if a local home improvement store has the blower to rent. It may also be worth considering calling a professional for best results. If you need a professional in Marin and Sonoma Counties look no further than the team at Home Stewards.

Foam Board

Another type of insulation is Foam Board. There are a number of different uses such as insulating a floor or an unvented low-slope roof. However, foam boards work well to insulate everything from foundation walls and basement walls to unfinished floors and ceilings. Foam boards and rigid foam panels can also be beneficial at reducing the amount of heat conducted through wood, wall studs, and other elements that make up a homes structure.

Many homeowners rely on this type of insulation for their home. Foam board is usually made of polyurethane, polystyrene, or polyisocyanurate and is part of both exterior and interior wall sheathing. R-values typically vary between R-4 and R-6.5 per inch of thickness. With that said, foam boards and rigid foam panels reduce energy consumption better than many other types of insulation on the market because of their relatively high R-value. Foam board is best used for unfinished walls such as foundation walls and basement walls, floors, and ceilings.

Despite it’s good air-sealing and R-Value, many are concerned about flame retardants in foam insulation. It can be difficult to cut to size if you’re trying to install it between studs, rafters or joists. All foam has a relatively high carbon footprint, and some use blowing agents that deplete the ozone layer or contribute to global warming.

Spray Foam

One increasingly common type of insulation application is Spray Foam. This type of insulation is primarily used to seal leaks and gaps inside existing walls. Liquid polyurethane is sprayed into the cavity of the wall, from there it expands and hardens into solid foam.

Spray foam comes in two primary types: open-cell foam or denser closed-cell foam. Closed-cell foam has one of the highest R-values of any insulation, around R-6.2 per inch, but it can be expensive and it creates a vapor barrier. Many projects cannot afford spray foam insulation, and in many climate zones it is inappropriate to install a vapor barrier in a wall or roof assembly. Open-cell foam insulation values are around R-3.7 per inch of thickness. When choosing spray foam to increase the R-value of a home’s insulation, consider calling a professional to do the job such as Home Stewards.

Spray Foam Application

Installation can be trickier than simply aiming and spraying. There are many variables that have to be right for successful application. There are many sob stories when spray foam has gone wrong, as it’s a costly repair that involves laborious physical removal. As with all foam products, there are some with concerns over the health impacts both during production and during the lifecycle of spray foam. Different blowing agents may account for some differences in Global Warming Potential, as well as long-term durability of the product. In unvented assemblies this is often the choice of contractors because achieving good air-sealing and vapor-retarding is much easier when the material is sprayed in a consistent layer over an entire assembly. In some unvented roofs, such as those found in mid-century modern Eichler homes around the San Francisco Bay Area, spray foam is actually being installed as a finish roofing material! It requires a final coating to protect the foam from UV, and the coating requires regular maintenance. In such applications beware of some critters that may dig into spray foam from the exterior, such as crows in Lucas Valley and Marinwood! Another potential downside is that foam is not as resistant to fire as compared to the original tar and gravel roofs installed by Joseph Eichler in the 1950s and 1960s.

Mineral Wool

Mineral Mineral Wool, also referred to as “rock wool,” is made of recycled industrial materials. These materials include rock and furnace slag which create superior thermal and acoustic insulation properties. Mineral wool can be included in batt, blown-in, or board products. An interesting fact or benefit to using mineral wool is it’s naturally resistant to flames (similar to fiberglass). Rock wool offers sound insulation with a relatively high R-value. It’s naturally resistant to insects and will not support mold growth on its own.


Reflective insulation reflects escaping heat back in the direction of your home’s interior. (Or keeps the sun’s radiant energy out.) By harnessing the loss of heat, in return it lowers your heating bills. During the summer months, it reflects the heat away from your home to lower your AC bills. Reflective insulation is often installed in the attic ceiling. This is done because it helps reflect sunlight and reduce the radiant heat transfer from the underside of the roof to the other surfaces in the attic. In affect it keeps your home cooler and more comfortable. Radiant barrier materials are also used around HVAC components and conductive pipes to create a more enclosed and efficient energy system. A radiant barrier requires an air gap in order to function effectively.

Environmental Considerations

Insulation plays its part by reducing the need for natural gas, propane, fuel oil, and electricity to heat and cool buildings. In reducing heating and cooling loads, insulation benefits the environment by reducing emissions of pollutants. Some of these  pollutants are carbon dioxide, sulfur oxide and nitrogen oxide, among others. Many of the environmental benefits of insulation are obvious. In a home or building, insulation reduces energy use. In return it reduces pollution and cuts down on water used in power generation.

While all insulation types generally reduce energy consumption. There are specific insulation types that can impact the environment differently in other ways. The embodied carbon (how much carbon it takes to create a material) and the global warming potential (which includes chemicals which increase global warming) of materials should be considered. Additionally, some materials require extractions or manufacturing of unique and/or dangerous resources. For example, fiberglass, mineral wool & cellulose all have the ability to recycle or reuse materials, however spray foam does not. Below are some of the factors that determine how environmentally friendly and energy efficient insulation is.

– Impact of insulation production on Global Climate Change

– Percentage of recycled content

– Reusability or recyclability

– Ecological impacts (e.g., water pollution, reproduction impacts)

– Health impacts on installers

Safety Considerations

There are many different factors to consider when working with different types of insulation. For example, insulators such as fiberglass batts, blown-in insulation, and spray foam can irritate skin and airways.  They can cause other health concerns as well which is why proper ventilation and personal protective equipment for eyes, hands, skin, and respiratory are required. It’s also extremely important and absolutely necessary to have a safe installation procedures. Replacing insulation in older homes could also put homeowners looking to take on the job themselves in direct contact with asbestos or lead paint.

Homeowners with older homes or damaged insulation should call a professional to ensure that insulation particulates are not spreading throughout the home. If you have indoor air quality concerns or need an Industrial Hygienist to inspect your home in the San Francisco Bay Area, Healthy Building Science provides extensive indoor air quality inspections & testing.


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