Insulation: Comfort In Rigid Form
We love visiting construction sites. We were most surprised and fascinated when we toured a subdivision in Eastern Florida and found that the exterior walls of the homes there were all built with concrete blocks. Hurricane country you know. Apparently, this wasn’t a problem for the interior finish carpenters. Furring strips and rigid insulation were added to the interior surface of the block creating a base for attaching wallboard and allowing space for electrical wiring, insulation, and yes, improved quiet as well.
More recently we visited our dear friend and fellow author Tim Green in Skokie, Il. He and his wife Allison opened their home – and their kitchen – to us and we enjoyed the most wonderful meal together. This was our first visit to their new place and naturally we were given a full tour. In the basement (most of it was finished) there were – you got it – block walls covered with furring strips and rigid insulation. You would think that someone would eventually come up with something new. Our point. If you have an unfinished basement or are planning an addition where block walls are required you may want to consider the configuration we just described. It seems to be popular everywhere. We suggest a layer of plastic sheeting between the block wall and the insulation to insure that moisture doesn’t make it past the block wall into the insulation layer.
Furring strips are used as a nailing base for wallboard and must run horizontally at the ceiling and floor and vertical strips must be placed on each wall in every corner and should be installed at a minimum of 2 feet on center over the remaining portion of the wall (16 inches on center is better). Furr strips must also be added around window and door openings. Keep in mind that the furr strips should be slightly thicker than the insulation being used. The folks at Johns Manville’s research and development center in Denver tell us that you can expect the equivalent of about R-7 per inch of rigid insulation. So, if you decided to use 2×4’s on edge as your furr strips you could expect an insulative value of R-21 with room to spare.
By the way, be sure to use redwood or pressure treated lumber for your furr strips. They can be attached to the wall with masonry anchors or powder actuated pins. We own a stud gun so that makes powder actuated pins our least expensive alternative. Especially since so much time can be saved by not having to do all of that masonry drilling. Check out the cost of renting a stud gun before you begin – you could find out it’s cheaper.
Caulking or foaming all connections also is very important. Cutting rigid insulation with a razor knife can leave ragged edges. Fill those spaces with spray foam and call it good. Yes, it is better to use a hand or circular saw and make a square cut all the way through the insulation, but what the heck. You decide on which method fits your toolbox best.
Your home is your shelter from the elements and its energy efficiency – and your comfort level – are elements of extreme importance. Your home also acts to protect your from unwanted noise. A quiet environment can reduce stress, enhance health and well-being, and increase productivity. As our world becomes increasingly urbanized, crowded and noisy, we have come to realize that sound control in the home is not merely a luxury, but a necessity. That’s why lots of insulation is a good thing.
Here’s some fun to know stuff about sound levels. Loudness is measured in decibels (dB). The decibel scale begins at the threshold of hearing (0 dB) and extends beyond the threshold of pain (120 dB) to levels that destroy hearing tissues (180dB), and beyond. Decibels are a proportionate measurement. For example: an increase of ten decibels is perceived as a doubling of volume. For example: A 50 dB sound is twice as loud as a 40 dB sound. If you have typical, healthy hearing, you cannot perceive an increase of 1 dB, you can barely perceive an increase of 3 dB, but you can clearly detect an increase of 5 dB. If you have typical, healthy hearing, you cannot perceive an increase of 1 dB, you can barely perceive an increase of 3 dB, but you can clearly detect an increase of 5 dB.
By the way, a standard wall composed of studs and drywall reduces sound from an adjacent room by about 30 dB. Adding insulation can eliminate another 5-7dBs. But, there is more to sound control than a basic stud wall filled with insulation. Adding an extra layer of half-inch wallboard can reduce sound by another 8dB. As you can see, creating a barrier that will reduce sound by 50dBs (the level that keep things on your side of the wall pretty quiet) isn’t very difficult to achieve. Ain’t life great!
Keep in mind that sound travels through a house just like we do – through one door, down the hall and through another door. Keeping sound out means dealing with these openings too. Make sure that each door is solid and fits tightly into its opening. And remember, air leaks are sound leaks as well. And, that’s all there is to it.