Crawlspace Insulation & Fire Codes
To the Editor:
I found the article on conditioned crawlspaces ("Building a Sealed Crawlspace," 10/03) very informative. As a building inspector in New Jersey, I have promoted this concept for years. The only disturbing thing about the column is that the use of uncovered rigid insulation in crawlspaces is prohibited due to the smoke development ratings.
Thank you.
Matthew O'Hara
Barrington, N.J.
Author Jeff Tooley responds: Our company has run into the fire code issue in our crawlspace work. Here's where things currently stand: Building departments in our area used to allow exposed extruded polystyrene to be applied over framing or concrete in unconditioned spaces. But once they realized that we were making the crawlspace a conditioned space, they started to require a fire-rated foam board. In response, we now use Dow's Thermax, which meets local code requirements, and we are not required to cover it. Thermax is a polyisocyanurate foam; it doesn't melt and has an ignition point near 800°F. It has foil facing on both sides and is reinforced with fiberglass, which makes it sturdier and helps it achieve a 15-minute fire rating. When the building departments cracked down on the pink and blue foam board, we had to go back to some homes under construction and cover installed board with drywall. I don't recommend drywall in a crawlspace at all, and the code allows other coverings (metal, wood, and rock wool), but I left that decision up to the builders who were paying for the work. Any covering is inconvenient and awkward, so we stick to Thermax, though any brand with a similar fire rating would work.
Nail Gun Injuries No Accident
To the Editor:
I read with great interest Ted Cushman's article on nail gun injuries (In the News, 10/03), in which he reported information from a study on nail gun injuries among residential carpenters. I conducted the study and would like to clarify issues raised in Mr. Cushman's report.
First, Mr. Cushman wrote that inexperience was reported as an important risk factor in our study. We did report a higher injury rate among apprentice carpenters (3.5 times higher than journeymen). This rate was based on the total hours each carpenter worked but not the hours they actually were using a nail gun. We believe the use of these tools is often considered a relatively unskilled task assigned to inexperienced workers, and we found evidence that apprentice carpenters use the tools more of the time than more experienced carpenters. It is important not to attribute the higher rate solely to inexperience when it may, in fact, be a reflection of their greater use of a potentially dangerous tool.
As Mr. Cushman reported, we recommend formal training for carpenters who use these tools. A number of injuries were the result of a carpenter firing the tool back toward himself, using his nondominant hand, poor placement of the non-firing hand, working in an awkward posture, and lack of eye protection, for example. However, we tried to emphasize how our findings support the need for engineering and policy changes to prevent these injuries. The majority of the injuries we investigated (68%) would likely have been prevented if the carpenter had been using a tool with a sequential trigger.
Our study was conducted before the industry-sponsored ANSI standard change (effective May 2003), which calls for the shipping of framing nailers with sequential triggers instead of contact trip mechanisms. Users can still request a contact trip mechanism. Based on our data, we would like to have seen the contact trip discontinued, but this is at least progress. Suppliers will often retrofit existing contact trip guns with sequential triggers, sometimes at no charge.
We know there are concerns on the part of contractors and carpenters about slower production with the use of sequential-trigger tools. We are interested in studies that look closely at this issue in a broader context; speed in sheathing may be offset by costs of extra nails resulting from unintentional firings of contact trip guns, poor construction quality, and costs of workers' compensation claims for injuries. We recently reported that nail gun injuries, along with injuries from falls, setting steel beams, and lifting framed walls, were among the most costly work-related injuries in residential carpentry (Journal of Occupational and Environmental Medicine, 8/03). Because many of these injuries involve relatively minor puncture wounds, their potential seriousness is often dismissed.
Finally, I find the use of the term "accident" to describe these injuries worrisome, because it implies that a random event has happened. These are not accidents, they are preventable injuries. It does not make sense to focus prevention on the training of workers in the use of a dangerous tool. The tool should be changed instead! We are smart enough to prevent many of these injuries, and we should.
Hester J. Lipscomb, Ph.D.
Associate Professor, Occupational and Environmental Medicine
Duke University Medical Center
Durham, N.C.
Commonsense Installation
To the Editor:
In the November 2003 Q&A, your expert advises against venting a bathroom fan through the soffit at the eaves because the moist air will "most likely" be drawn back into the attic.
A dose of common sense might be in order. If the fan has any kind of velocity at all, will that moist air really make a hard U-turn and streak into the attic? And if the suction up toward the ridge is that impressive, will the moisture even have time to condense on a cold surface before it blasts out the ridge vent? I'm wondering if I need to fit my cap with a chin strap the next time I'm working near a soffit vent.
So many bathroom fans are either poorly vented (into the attic or a joist bay) or not vented at all, getting that moist air to the outside, even if it's in proximity to the soffit vent, is an improvement.
Arne Waldstein
Arne Waldstein Construction
Housatonic, Mass.
Likes Fiber Cement
To the Editor:
I liked your article on fiber-cement board ("Installing Fiber-Cement Siding," 12/03); it's nice to see that there is someone else out there who installs correctly. I'm in the siding business in Wisconsin. We do a few big homes on Lake Michigan each year in Hardiplank. It is by far a superior product compared to others. You can mix and match your corner boards, light blocks, and other components. When we want higher definition at the corners, we use MiraTec, which blends well with Hardiplank. There is really no limit to what you can do with this product.
Randy Westphaln
R.W. Siding Specialist
Twin Lakes, Wisc.
