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Green Building Curmudgeon

Historic Preservation and Green Renovation

Much alignment and little divergence between the two disciplines

The title of this guidebook is a mouthfulThe Secretary of the Interior’s Standards for Rehabilitation and Illustrated Guidelines on Sustainability for Rehabilitating Historic Buildings — but it contains a lot of good information on making historic properties efficient and sustainable.

At a recent round-table meeting on sustainable historic preservation, I was struck by how much alignment there is between preservation and green renovation. Now, green renovation is a wide and diverse field, and some of the deep energy retrofit people probably don’t have the same opinion on sustainable preservation standards as I do, but disagreements just help to keep things interesting and further the conversation.

I certainly have my issues with historic commissions. In fact, my local group managed to cause enough delays in approval of a new house for myself that I have put the whole project on hold until the economy picks up.

The Secretary of the Interior’s rehab standards

Following the discussion, I located a document that the speakers referred us to The Secretary of the Interior’s Standards for Rehabilitation and Illustrated Guidelines on Sustainability for Rehabilitating Historic Buildings. (Man, is that a mouthful!)

The book (or pdf document if you prefer) is a reasonably well thought out guide to making appropriate decisions on sustainable rehabilitation projects. It was designed to expand on and replace a small chapter on Energy Conservation in earlier guidelines.

The guidelines appropriately recommend doing building diagnostics before undertaking energy efficiency work – always a good idea. They prioritize weatherization appropriately – insulate attics, insulate crawl spaces, and fix air leakage before insulating walls and replacing windows.

Saving old windows

Speaking of windows, this is probably the biggest issue with preservationists – they look to save existing historic windows in almost all cases, with very few exceptions. Recommendations for existing windows include repairing sashes, adding weatherstripping, and adding interior or exterior storms to improve performance – steps which very often provide better value and are overall as sustainable as, or more sustainable than, window replacement.

The guidelines promote operable windows for natural ventilation, open porches, shutters, and awnings for shading and passive cooling, vestibules, the use of natural light, and low VOC finishes. Some other key concepts they promote, all very logical, include not insulating wall cavities that are susceptible to water infiltration and installing renewables only after all efficiency improvements are implemented. I like the way they think!

What about spray foam?

I found only one area where they guidelines and the speakers at the round-table separate themselves from standard green renovation practices – their fear of foam insulation. The major issue is their concern with reversibility, followed by a fear of creating moisture problems by using it.

On the first issue, I believe that they are not properly distinguishing between low-density and high-density foam. Low-density (or open-cell) foam can be removed without damage, and while it may leave some residue that non foam insulations don’t, I don’t believe that it should be dismissed out of hand. High-density or closed-cell foam is often more difficult to remove, and while I don’t fully agree with the concept of reversibility, I will concede this point to the historians.

On the second issue, two speakers at the round-table responded to a question about spray foam insulation by stating their view that it often traps moisture and causes structural damage. In addition, the National Trust website states, “Spray foam insulation … can hinder airflow and lead to the rotting of timber-frame members.”

While this issue is not explicitly stated in the guidelines, it is often repeated, I feel incorrectly, by preservationists. Spray foam is one of the best ways to improve the performance of an existing building, and when installed correctly and in the proper location, won’t create any more moisture problems than any other type of insulation.

Here is to hoping that in the name of better building performance, there may be some flexibility in their future guidelines.

Old thinking is new again

In doing research for this post, I ran across this short piece on windows on the National Park Service website, which I think provides a good guide for sustainable design: “Early builders and architects dealt with the poor thermal properties of windows in two ways. First, the number of windows in a building was kept to only those necessary to provide adequate light and ventilation. Second, to minimize the heat gain or loss from windows, historic buildings often included interior or exterior shutters, interior venetian blinds, curtains and drapes, or exterior awnings.”

Given how many buildings have too much glazing, much of which isn’t operable or effectively shaded, it seems like our forefathers had some pretty good ideas about how to build right.


  1. Expert Member
    Dana Dorsett | | #1

    Low density open cell foam vs. non expanding injection foam.
    One aspect of low-density foam in a historic timber-frame is the potential for blow out or cracking of plaster using half-pound pours in wall cavities, whereas non-expanding injection foams (often used as CMU core fills) don't have that issue. The also tend to have higher vapor permeance than half pound polyurethane, and higher R/inch, which can be a double-edged sword in cold or very cold climates, but a drying-enhancer for most of US zones 4 or lower.

    I've never tried to remove this stuff though- not sure if it's as easy as with open cell polyurethane.

  2. ZCau4GnZ5T | | #2

    Spray Foam Insulation and Air Sealing
    One objection to spray-in-place foam for insulating (all performance issues aside) is the fact that it can permanently obscure historically-significant carpentry/joinery details, depending on where it's applied, like within the rafter bays of an historic attic. This is why most preservationists advocate insulating attic floors instead, despite the increased challenges of air sealing floor penetrations.

  3. wjrobinson | | #3

    Hysterical zones? Preserve
    Hysterical zones? Preserve that joint? Green?

    Interesting ways of looking at things.

    Imagine a huge push to preserve orientated strand board in some future day......... Or even...... Spray foam!@@@@@!!!!

  4. dankolbert | | #4

    Come together.....
    I agree that it's gratifying seeing "green" and "pres" coming together. One of our local heroes, Peter Taggart, has been making the connection for years, and is active in both worlds. It's a big issue here in northern New England with our very old housing stock.

    I am more in the Pres folks' corner than yours on the spray foam issue. I'd rather see polyiso sheets cut and foamed into place than a wholesale foam job.

    To me, one of the most contentious issues that I don't see much addressed is how RRP and historic pres are supposed to work together. We are often faced with the conflict between preserving original stock and meeting the mandates of the RRP regulations. I don't have any great solution to the problem.

  5. Expert Member
    CARL SEVILLE | | #5

    Window Preservation Collaborative
    Just ran across this website of the Window Preservation Standards Collaborative, a group of professionals who are creating standards for improving existing historic windows. Seems to fit well with the subject of this post.

  6. zt88TUzzpw | | #6

    The concept of preserving a building carries with it a key tenant of green building - reduction of the use of virgin materials. It's great to see that the historic preservation movement has, for years, been moving to focus on greening these buildings through energy conservation methods. Great analysis of the reference guidelines.

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