NAPC Green Guide

www.cleanair-coolplanet.org/for_communities/HDCGuide.pdf.

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Insulation

Does no one but me worry about retrofitting walls with insulation anymore? The recently circulated PA for Weatherization includes allowing blown-in insulation. We had a terrible experience where insulation had been installed with no moisture barrier in early in my career, which allowed significant condensation and resulted in widespread termite damage to an NHL. I have always been very reluctant to insulate, preferring to do ceilings and floors, and relying on a good caulk job to reduce wall infiltration. Of course, I am working in Alabama, where the payback on wall insulation is more than 50 years.

Arkansas: I agree that adding wall insulation to intact walls is problematical and has potential to damage historic fabric. Our transitional Arkansas climate makes it difficult to choose a ‘best’ side for vapor barriers. In addition to adding moisture, foam insulation expands and can put pressure on structure and materials. Other fills settle and boring exterior holes in siding introduces multiple places to decay. From my energy auditor experience during the previous energy crisis, adding ceiling insulation, caulking cracks to lower infiltration, and adding storm windows provides the most reasonable solution for most buildings.

Illinois: Wall Insulation and Historic Buildings: Retrofit Options

The renewed push for energy efficient rehabilitation is bringing the topic of wall insulation into the forefront. In the last week several states have commented on the Programmatic Agreements that are being developed for weatherization programs. Incentive programs such as weatherization funding are the current subject, but the real issue is that of defining the best practices for energy retrofit of historic houses. There is actually quite a bit of agreement on this subject, and new analysis tools coming from weatherization programs. Weatherization professional in Illinois rarely promote window replacement because the cost doesn’t justify the payback, and they have good tools to prove this. Operational and behavioral changes such as programmable thermostats are first on the list. Air sealing following a blower door test is also a high priority. Attic insulation is everybody’s the first priority for insulation. Equipment changes such as new heating and cooling equipment are next. New furnaces with combustion air intakes that eliminate the need for a chimney reduce infiltration. Wall insulation is a much lower priority and window replacement is near the bottom in terms of cost payback.

Wall insulation can be a cost effective strategy for energy efficiency because there is a lot of wall area. If the preservation community insists that walls should not be insulated, we are going to have houses that are much more expensive to operate, and this is going to get worse as energy costs rise in the future. Uninsulated walls also means less indoor comfort. Our standards of comfort means we are used to walls with warm interior surfaces.

This is an important issue for the preservation community to address with both good building science and knowledge of readily available technologies. Just for the record, old houses statistically need to be made 35% more energy efficient just to equal the average home efficiency today. As efficiency standards increase, older homes are going to be perceived as even worse. If we want historic resources to have viable economic lives into the future, their energy efficiency is a real issue.

The source of the concern about insulation goes back to the 1970s. There were concerns about expanding foam insulation that was a physical damage. There was also a lot of effort given to the placement of vapor barriers, for which there were few options when existing wall assemblies were being maintained.

The National Park Service web site includes the following section on insulation, which comes from the 1970s era of building moisture science:

http://www.nps.gov/hps/tps/weather/insulation.html

This document state that “Adding blown-in insulation to historic wall assemblies may trap moisture within the wall and lead to accelerated and often hidden deterioration of the structure.”

This is a very misleading statement. It sounds like the building materials are a dam and holding back buckets of water through condensation. The moisture that is at issue is that of moisture vapor and increases in the moisture content of materials, primarily wood. This is not about condensation. The new chapter of Building Envelopes in the ASHRAE Handbook Applications states that condensation is possible only on materials such as glass that are not porous or hygroscopic. Condensation is undefined for capillary materials. Some things are possible, but condensation is not one of those things.

Updated Research on this topic:

The Fall 2005 issue of the APT Bulletin featured an article by Bill Rose entitled “Should the Walls of Historic Buildings Be Insulated.” Bill Rose is a research architect at the University of Illinois at Urbana-Champaign and the author of Water in Buildings. He knows his stuff and is very active in the world of historic preservation. This article is available on the www.jstor.org web site. (Free to APT members and lots of others) [Note for the record, I was the editor of this issue of the Bulletin.]

http://www.jstor.org/pss/40003158

In his conclusion to this article, Bill states that “if the exterior materials are robust, they should withstand the addition of insulation with little change in service life or maintenance.” Some updated thoughts on this analysis.

1) In what climate region is the building located? There is not much of an issue for buildings in hot/dry or hot/wet climates. Wetness in exterior materials is associated with cold winters, particularly in sub-freezing periods. When exterior building materials don’t get that cold, there is little potential for moisture content increases. This is mostly an issue in cold climates such as the northern half of the US and virtually all of Canada.

2) There are big differences in masonry building versus wood-frame buildings. Since most older masonry buildings have three-wythe thick brick walls, the exterior walls are pretty “robust.” Adding insulation to the exterior walls means covering up interior surfaces, moving trim and a decrease in room proportions. While the brick themselves may be robust, the wooden ends of joists sitting in masonry pockets can act as a thermal bridge. There is legitimate concern about the long term effects of insulated interiors and effect on the joist ends in masonry pockets. This is a topic that deserves further research but there are lots of examples where this has been done. There is a good article on this topic in the Building Science web site and this was also a major discussion at a recent APT NY meetings:
Energy Flow Across Enclosures by Joe Lstiburek of Building Science Corp.

http://www.buildingscience.com/documents/insights/bsi-028-energy-flow-across-enclosures

3) The primary concern that is most common is that of wood frame buildings where the existing wall assemblies(plaster, studs, sheathing, clapboards) are being retained and insulation is “blown” in to the cavity.

Where are we at today?

1) Blown in cellulose insulation that is treated with fire-retardant salts is the most reversible material to install and has good insulating properties. Spray foams are more difficult to control and are less reversible. Spray foams should be used in discrete locations for air sealing as they work very well for this purpose.

2) The primary effect of additional wall insulation is that the exterior materials will be colder in the winter, which also means that they will be have a higher moisture content, aka “wetter.” This does not mean condensation. The higher moisture content does not lead to freeze/thaw damage in wood, which is more of a concern for masonry materials. Old growth wood that was typically used on historic homes is more “robust” than modern wood and modern wood composites. Documented problems with exterior wood materials in insulated buildings appear more common in modern buildings than in historic structures. The higher moisture content in materials is not favorable to mold when these materials are cold, as mold needs temperatures above 50 degrees F. The exterior sheathing and clapboards of older wooden buildings generally allow enough air infiltration to help mitigate some of the effect of the moisture content changes. There can also be a differences based upon a wall orientation, as south and west walls are more subject to winter temperature oscillations than east and north walls. There is also evidence that the problem is somewhat localized with greater impact on the exterior walls at bathrooms and kitchens, which have higher interior moisture sources.

3) There will be a greater impact on the exterior paint than there will be the wooden materials, which is likely to increase the repainting cycle for clapboard exteriors. For exteriors in good shape without lots of layers of paint this should not be a major problem. For exteriors with deteriorated paint or those that had previous paint jobs with poor preparation, this will accelerate the need for a major exterior preparation and repainting. The big question is “what is the frequency of repainting change from what would be a normal cycle? This question does not have a definitive answer.

Iowa: In Iowa, we do not recommend wall insulation unless the entire warm wall covering needs to be removed (such as a result of flood mitigation work). If installed, we comment on the need to create a warm side vapor barrier. At the present time we are also very concerning about spray foam especially on the underside of roof rafters because of potential trapped moisture issues. Until research indicates a change concerning the harmful effects of wall insulation, we do not recommend.

Ohio: The use of side-wall insulation has been a concern throughout the discussion about these programs in Ohio. We asked for technical assistance from ACHP during conference calls they held among SHPOs, but got no response. We also expressed our concerns about the treatment of this issue in reviewing the draft Prototype PA, but the exemption was retained in the final version.

Ohio had already been involved in negotiations for a statewide PA for several months before the Prototype was issued. We ultimately chose NOT to include Weatherization projects in the PA. This was due entirely to the unresolved issue of the longterm effects of side-wall insulation, despite repeated suggestions from state program staff that our knowledge on this issue was outdated.

At this point in time, a partially signed statewide PA for the EECBG and SEP programs is currently in DOE's hands, but they have indicated to us that they are reluctant to sign any PA that doesn't include Weatherization, as a matter of policy. DOE even suggested that the state agency should change their program to address our concerns, but that's unlikely given that the grantees all need to complete a specific number of projects in conjunction with deadlines in their grant agreements.

Our recommendation to DOE has been that they should formally ask NPS for an advisory opinion about whether the sidewall insulation component of these projects can be made to meet the Standards, perhaps through the use of a vapor barrier coating or some other means. We stressed that this request wasn't limited to concerns from Ohio, but that it was based on recommendations in the NPS guidance that all the SHPOs are required to use under the regs. I would encourage any state that's currently involved in discussions about this issue to also ask their DOE counterpart to take the initiative and ask NPS for a specific technical opinion on this issue, based on their program's specifications for this practice. If nothing else, it's been our suggestion to DOE that the program should be monitored and studied over time to see whether what happens with these projects fits within our experience of this practice.

South Carolina: We are also concerned. We are working with our State Energy Office to address all the aspects of the prototype PA as well.

Having just finished a presentation where our office (me) and the Energy Office staff spoke on Greee Preservation, we are seeing some places where our standard advice may shift slightly. At present, we are considering changing our "Not Recommended" approach on insulation in frame walls to a "Strong Warning" approach. Since we are still in consultation about this, I can't give you a finalized comment.

One of the points that the Energy Office staff have made clear to us is that the advice about a vapor barrier on the warm-in-winter side of the cavity is NOT good advice for the warm humid climate of South Carolina - similar to your climate I would think.

I still need more discussion with the Energy Office folks before I can speak with conviction on this but just know that others of us are in the same place as you describe.

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Sustainability Survey

Green Downtowns

I am in search of communities who have created a "Green Downtowns" program, an effort we are developing here in Maine through a partnership with our Main Street program, Statewide preservation organization and a private foundation. Loosely defined, this involves everything from the obvious building retention and recycling to tree planting, urban trail development, public litter recycling, creative public education/outreach campaign and local leadership development. Good examples, fresh ideas and suggestions are needed. Thanks!

Green Roofs

Illinois: Chicago's City Hall does have a green roof...here's a few links for more info.

Maryland: Please see this article about the green roof on the Montgomery Park building in Baltimore City This rehab was assisted with state (and probably federal) rehabilitation tax credits.

Massachusetts

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