Crawl Space Insulation

This Crawl Space Insulation article was written in reply to a question which was sent to towards the end of September when a visitor used our Have Your Say page. This question comes from Mrs R in Tennessee who prefers to remain anon:-

"My home is 3 years old, and the subfloor is insulated with fibreglass. I would like to have it all removed and replaced with liquid foam insulation. I have two questions please, (a) My house is on a crawl space, will the liquid foam insulation be affected by moisture or humidity? and (b) I live in a very small town, and have not been able to locate a company that will give me an estimate, and/or do this job. Can you send me a contact link or two?"

Hello to Mrs R. and anyone else who may be planning their own crawl space insulation project. The end of summer is typically when many homeowners start to think about crawl space insulation and it is also when it becomes more difficult to find an available qualified insulation contractor to assess your space and do the best home insulation job for you and your home.

This is an important area which can easily be your biggest energy eater as insulation work to the crawl space or basement area in a home is often left completely behind in favour of the more popular loft insulation and cavity wall insulation projects. Who could believe that it is possible to lose so much hard earned heat from your home - through ground floors!.

Traditionally rigid insulation or batt insulation has been used in crawl spaces when friction fitted under the floor between the floor joists and held in place - and more often because of building codes, crawl space ventilation vents, etc. this form of insulation is still the best option, often by adding to existing insulation and thus improving the R-value to the maximum.

Liquid Foam Insulation

Liquid Foam Insulation is sometimes used to insulate crawl space exterior walls from the inside but there are a few if's involved,

here are some more obvious ones:-

  • if your local building code allows,
  • only if the crawl space is NOT ventilated,
  • if the space is dry throughout the year
  • AND only if the floor above is not insulated.

Not all liquid foam insulation is the same. If you are looking for material type that is especially resistent to dampness and moisture you would probably be better off with "Icynene foam" which has high resistance properties to water intrusion - although there are others and your local certified insulation contractor should have good options.

Whatever material you use to boost the R-value of insulation in your crawl space, it is important to remember that the use of Liquid Foam Insulation requires certification (which you definitely want to back up any potential increase in the value of your home) and foam should only be installed by a qualified contractor.

There are huge advantages to having your home assessed by an insulation expert who will then be able to give you the best "up to code" insulation option for your home and your budget. This is the address of the web site of the Insulation Contractors Association of America

- or you can copy and paste the following into your browser:-

- and on that page you are asked to give your area code to located a certified qualified insulation contractor near you.

Other Crawl Space Insulation Options

Regarding insulation - going liquid is not necessarily the best option - as not all rigid or batt insulation is the same, you may be able to upgrade your R-value by using a product that is not prone to absorbing moisture.

Insulation that is wet or damp becomes compressed and is useless in insulating your home, whereas for example, materials like Cellular glass are waterproof and impervious to water vapour. Its also nice to know that this material is stable, won't burn up and rats and mice don't particularly like it...

Off the top of my head here are a some pointers to keep in mind while planning this project, which should go a long way to explain why I would only recommend a professional onsite assessment prior to installation:-

Crawl Space Insulation Pointers

  • The climate you live in will determine the type of crawl space insulation options that are open to you.

  • Your geographic location will also determine the recommended minimum insulation R-value that should be applied.

  • The general direction your house faces.

  • The drainage around your home.

  • Your local building code.

  • The age of your home and the type of construction are important factors as well as and if wooden frame or metal frame has been used in construction. As your home is relatively new - does it have built-in insulation within the foundation walls.

  • The condition and R-value of the present insulation and if it would be more cost effective to leave it in place and add more to increase the insulation without over insulating and compressing the material.

  • It is very important to know if the crawl space is ventilated or not - traditionally building codes required the installation of vents during home construction but in many areas this is now no longer the case and vents are being blocked.

    There are two ways to find out - your local building office will be able to advise you - and a qualified insulation contractor will know the building code requirements for your home type in your area.

  • Unventilated crawl spaces allow for insulation of the crawl space walls as an option to insulation suspended below above floor structure - but only if the space is dry throughout the year AND the floor above is not insulated.

  • Do you have a durable vapor retarder like a thick polyethylene film properly installed on the ground area over all of your crawl space - this is a very important factor in reducing the amount of moisture that gets into the space.

  • Spray foam insulation may also 'by code' require the additional installation of an air barrier.

  • Get that valuable certificate proving insulation work done on your home.

It is important to remember that building codes provide us with the minimum recommended - the minimum, as in this R-value given for your area is the minimum you should install and wherever space and budget allow - one should aim to install the maximum that can comfortably be installed in your home.

Eco Friendly Insulation

More and more homeowners trying to reduce the harm that we cause to the ozone layer, will seek out foaming agents that do not use Hydrochlorofluorocarbons (HCFC's), or the even more harmful Chlorofluorocarbons (CFC's).

The frequently used Polyurethane or the Polyisocyanurate are both liquid foam insulation types that are based on a low conductivity gas (usually derived from HCFC's) - they are popular because the give a relatively high R-value of somewhere around R7 or R8 - at least until the gas escapes and the R-value drops a good couple of notches.

Thankfully it is also becoming more and more important to buyers that not only is a home effectively insulated but the the materials used are eco friendly insulation materials that are as natural and have been prepared in the most environmentally friendly ways possible.

Many are becoming aware of the balance of installing insulation to help reduce energy needs and costs - and installing insulation materials that are manufactured in a way that in itself produces high carbon emissions - it is a very real delima that can only be solved by installing more eco friendly materials.

Homeowners are more and more often seeking "zero Ozone-depleting potential" insulants, like thermal efficient natural, organic or recycled materials as insulants to use in their homes.

Air Leakage & Ventilation

Regarding air leakage - it is also important to pay careful attention to the skirting boards to make sure that there are no unsealed air leaks and that all holes allowing pipes to travel up into your rooms are properly sealed.

If crawl space ventilation is a requirement for your home and your area, make sure that the ventilation openings are clear both inside and outside - it may even be beneficial to actually build a protective vent well if your vents are very near ground level.

Further Insulation Information

I hope that this information at least points you in the right direction, If you are looking for further indepth information may I suggest the following:-

  • Department of Energy Insulation Factsheet - available in PDF format

  • North American Insulation Manufactuters Association

  • You can get more detailed information on insulation options at the US Department of Energy, Energy Efficiency and Renewable Energy article on Sprayed-Foam and Foamed-In-Place Insulation - just copy and paste the following web address into your browser:-

Sorry, it seems that I am not able to write a short article!! - and anyway... there is just so much so say on the subject of ever developing crawl space insulation options.

I hope that you all manage to get your crawl space insulation project completed before winter sets in.
Best Building wishes to you.

p.s. If you have any relevant crawl space insulation experience with regards to crawlspace or basement moisture solutions, materials successfully used or information on insulation installation techniques which would be beneficial to the rest of our visitors, it would be great to hear from you, why don't you contact us and tell us your insulation story.

Related Insulation Articles

Resources  About Us  Contact Us  Privacy Policy  Site Map

© crawl space insulation All Rights Reserved