You oversimplified the discussion: How much insulation is “enough”?
Your recent article “Spray Foam: What Do You Really Know” (FHB #204) touched on an important topic that seems to be rarely covered: the diminishing return that comes from increasing the thickness of spray-foam insulation. What could have been a great opportunity to discuss how to rationally decide how much insulation is “enough” was presented simplistically, as a matter of two people’s opinions.
We are told that Chris Porter, the building-science and code manager for BioBased Insulation, says that 6 in. of open- or closed-cell foam “is perfectly adequate” in most parts of the country. Builder Michael Chandler, on the other hand, says that he’s OK with “$3000 for the additional 2% in performance.” Both of these statements are overly simplistic. Porter appears to be unconcerned with an almost 2-to-1 difference of insulating value between the two types of foam, and Chandler is ignoring what that extra $3000 might buy elsewhere in the house.
The rational approach is to do a cost/benefit analysis. Calculating heat loss is pretty straightforward, and therefore, we don’t have to rely on blanket statements like these to make sound decisions.
—David Strip, La Jara, New Mexico
Is R-40 not twice as effective as R-20?
I was confused by some of the information presented in Rob Yagid’s article on spray-foam insulation. A caption for the graph that compares efficiency to thickness states, “As the thickness of insulation increases …, the insulating value … diminishes drastically.” Now that can’t possibly be true! If R-40 is not twice as effective as R-20, then how much more effective is it? The caption would have us believe that R-40 is less effective than R-20.
—Steve Houlihan Santa Cruz, California
Associate editor Rob Yagid replies:
You’re right; the caption was misleading. However, the chart was accurate. When it comes to insulating a home, more is almost always better, and I had no intention of suggesting otherwise. But the fact remains that insulation reaches a point of diminishing returns, where the cost of the material exceeds the cost of the potential energy savings. When assessing the true performance of a wall or roof assembly, the labeled R-values aren’t always reliable, and the return on investment of the insulation is important when you’re building an energy-efficient home on a real-world budget.
We need numbers to determine greenness
With regard to the house on p. 58 of your Houses issue (“Rural Landscape, Modern Sensibility,” FHB #203), I would have loved to have seen a comparison between the total household energy usage with the original propane furnace and the total energy household usage since converting to the geothermal heating system—not just dollar comparisons, which are subject to regional variations, utility subsidies (as in the case of the featured house), and commodity price fluctuations.
Likewise, it would have been interesting to find out what the carbon footprint of electricity is in that part of Michigan so that I could better gauge whether switching from a 95%-efficient propane furnace to electrically powered geothermal heat was as “green” as it was made out to be in the article.
This may come across as nerdy quibbling, but it seems to me that if green building is going to be an editorial priority of yours, you should make an effort to give us some real numbers.
—Paul Eldrenkamp, via email
Organic can be toxic
On p. 34 of your annual Houses issue (FHB #203), Jefferson Kolle describes a cleaning product, as “… organic, so it is nontoxic, noncaustic, noncorrosive, and nonacidic.” I would like to introduce Mr. Kolle to methyl vinyl ketone to see if he still believes that all organic compounds are harmless, as he implies.
Methyl vinyl ketone is an organic compound used in the manufacture of plastic polymers. It is highly flammable, is very toxic if inhaled or swallowed, and causes burns.
So suffice it to say that using the label of “organic” is not the same as using the label of “nontoxic, noncaustic, noncorrosive, and nonacidic.”
—Charles Graham, via email
Excavate basements carefully
In his “Drawing Board” piece about finished basements (FHB #202), Kurt Lavenson suggests a bunch of good ideas, including excavating the foundation to make room for windows and doors to gain natural light. Readers in climates cooler than California should beware, however. Local frost depth and existing footings should be explored thoroughly before any adjustment of grade outside the house is considered. Removing soil reduces frost protection and could easily cause cracked foundations or worse.
—Randall S. Walter, Walpole, New Hampshire
Code clarification for efficient lighting
Lynn Underwood did a good job of pointing out some pertinent code changes in “Green Yesterday, Code Today” (FHB #204), but made an error when it comes to the requirements for more efficient lighting. Lynn states, “The code also demands that all recessed lights meet an ASTM manufacturing tightness standard and be sealed with a gasket or caulk …” (code section N1102.4.5). In fact, this change does not apply to all recessed lighting, but only to recessed lights that penetrate the building’s thermal envelope. With recessed fixtures in a drop ceiling, for instance, the requirement does not apply.
—Le Hitchcox, San Rafael, California
How Tyvek works
On p.16 of the July 2009 issue (FHB #204), the “How It Works” on vapor drive shows a cross section of a wall with Tyvek housewrap installed between the sheathing and the siding. I noticed that the wrap is installed with the printing facing inward, toward the sheathing. Is this correct? I am in New Jersey and just wrapped a portion of my home with Tyvek facing out.
—Kenneth Verbeyst, via email
Editor Brian Pontolilo replies:
To my dismay, you caught something we should have. The only reason we show the printing on our illustration in the first place is for that layer of the building assembly to be easily recognizable as housewrap (Tyvek being the Kleenex of housewrap). According to DuPont’s Web site, Tyvek housewrap can be installed in either direction. However, it is important to note that that may not be true for different types of housewrap.
Btu: You blew it again
In your last issue (FHB # 204), Larry Cler wrote a letter to correct a mistake in “Is Your Heating System an Energy Beast?” that you made labeling units of energy. His letter was explicit and accurate, but in the last sentence, you blew it again. The sentence reads, “1 watt equals 3.4129 Btu/hr or 1 watt/hr equals 3.4129 Btu.” It should have read “1 watt-hour equals 3.4129 Btu.” Energy is the product of power multiplied by time. My bet is that Mr. Cler had it right (he did), but that the magazine copied it wrong (we did).
—Nils Omholt, Sterling Heights, Michigan
Icynene’s pour fill is for empty walls only
Your spray-foam insulation story (FHB #204) is generally a well-researched and well-written piece. However, you got one item very wrong. The article states that Icynene has pour-fill products for existing walls, which is correct. However, it goes on to say that “The foam compresses fiberglass batts …” This is not true for Icynene’s pour-fill product. Icynene’s pour-fill formula should be used only in empty wall cavities.
—Teresa Crosato, marketing communications supervisor, Icynene
Countertop cost correction
In “Amazing Countertops” (FHB #198), and most recently in FHB’s Kitchen & Bath Planning Guide , the cost of Alkemi’s resin and aluminum countertops is listed incorrectly. The price printed reflects the installed cost, not the cost of the material, as noted. Fabricators can purchase the countertop material for $39 to $60 per sq. ft.
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