Deep Energy Retrofits, Historical Properties, and the Conversation

Recently a group of us started an interesting conversation on Deep Energy Retrofits (DER) & Historical Homes that spanned Twitter, blogs, and a whole host of other social media platforms with a ton of useful links. While the terms holy war, invaders, and boxing match came out of it, so did some great questions & thoughtful answers. As a builder, remodeler, energy modeler, deep energy retrofit fan, and closet preservationist I guess it time I added my wooden nickel to the conversation while hopefully adding something useful to it and some of the questions posed.

What is a DER?

Is it just a number, a concept, a certain process, or a combination of factors? So far we have had heard numbers ranging from 30 to 90% along with talk about health, safety, & comfort. As a builder / remodeler it is quite simple, it is first & foremost a project which is all about the customer’s goals, health, safety, comfort, and yes – the budget. While a regular retrofit maybe seen as replacing old obsolete items, when one gets into a DER though the concept changes.

A DER isn’t about just reaching a certain number, using specific products, replacing an item, or slapping band aids on an issue, but rather it implies a comprehensive inspection being done, a plan being developed, with the culmination of opening &/or accessing the areas needed to properly fix the energy related issues buried deep like insulation, ducts, etc… I must also add that in my book in order to qualify as a DER, the house should also be brought up to meet or exceed current energy codes. For some newer homes, 30% might be the limit, whereas some older ones might easily be around the 50 to 70% mark.

What makes a building historical?

Per the NPS (National Parke Service), a building generally must be over 50 years old to qualify & must also meet certain criteria. That criterion is actually one the most important pieces to consider before any work is done on the property. Was the property listed because George Washington spent the night in a room there (i.e. the interior is the most important), is it because of the architecture, the first time X was used, or??? This might help prevent the shell shocked look when someone says “Peter, we don’t care about the inside.” (Great response by John Poole on this question)

Who’s Historic Values?

As a reminder, “owners of private property listed in the National Register have no obligation to open their properties to the public, to restore them, or even to maintain them, if they choose not to do so. Owners can do anything they wish with their property provided that no Federal license, permit, or funding is involved”. The National Register only “encourages citizens, public agencies, and private organizations to recognize and use the places of our past to create livable and viable communities for the future”.  (National Register of Historic Places PDF Brochure)

While the “Feds” generally hold no control over what one does to the property (minus the caveats above) the control each state, county, city, and other local groups or committees has can be dramatically different and herein lays the issue for many. While one group (like the 1879 remodel pictured) almost wanted to hand us a medal for getting the vinyl siding removed (that a prior owner installed), others would have stonewalled us for months on the replacement material and colors which would have meant the vinyl stayed & was simply patched. (NPS NR brochures, FAQ’s, & guidance docs)

Who’s being unreasonable?

You want to add how much space to the exterior… Depending on the reason for the historical designation – I will generally side with the preservationists on this within reason. Generally a ½ to ¾ bump will not be noticeable so that one can apply some sheathing & drainage wrap (assuming skip sheathing wasn’t used). Not only does this improve the structure but it allows for the siding to still breathe & dry out. For the DER guys, by utilizing Closed Cell foam & possibly a SIS (Structurally Insulated Sheathing) you know have an R27 assembly. (Sorry if you think that a 4” foam exterior & cellulose installation is the only way to go – remember this is about the goals & best way to achieve them)

Everything is rotted and un-repairable so we were thinking – HURUMPH – Well it needs to be the exact same material & hung the same way… Can I get away with a bite me on this? In all seriousness, there is no such thing as the “same material” now-a-days. Whereas a board used to have 30 growth rings per inch, most now only have 3 – 8 rings which means that they absorb water more readily, are not as strong & deteriorate quicker.

Todays “same material” versions can have a major impact on not only the life of the product, but also the house if you do not account for those changes. Granted you can paint all six sides, but that still requires a way with dealing with water that can form or get behind it. If you want something to look as good & last as long as the original, you are looking at composites. Besides when one looks at the Secretary of the Interiors Standards for Rehabilitation (Pg. 7) it doesn’t say all, or you must but rather “The following Standards are to be applied to specific rehabilitation projects in a reasonable manner, taking into consideration economic and technical feasibility”.

Whatever you do must be reversible… I just love this one, which generally comes with the following; look whatever you do, you must be able to reverse it later – so no foam, just cellulose or fiberglass… First, no matter what product is used you will have to reopen the wall to remove it, & when you couple that with everyone’s belief that the wall assembly will get wet – why are you insisting that a sponge like material be placed inside the wall? Now I am not saying foam is the only option as there are numerous places & times other items will work great. In some cases though (especially where the bays are the drainage plane) that you are just asking for trouble unless you either leave it alone or deal with the issue.

Foam might cover up some historical detail… Inside a wall assembly, hidden from site, that had knob & tube tacked to it, and? Actually I can see this being valid for some beams buried in the walls & the solution is quite simple and that is to work together & get any areas photographed & documented.  Maybe cover the area with some foam board, tape, wax paper or plastic to that one area so that it can be inspected later.

It isn’t worth it / does the cost justify the means… I really do love watching the experts talk about ROI, simple payback periods and watching them continuously miss the boat. Just like it is rare for someone to buy a granite countertop because of payback, many people own historical homes for a multitude of reasons. Granted there are areas where older historic houses are bought because they are cheap & affordable, but for many people – they fell in love with the charm & character. Many of these start considering themselves stewards of these properties looking at long term fixes and ways to ensure they will be left to future generations.

  • John Nicholas

    Sean,  Thanks for the post and continuing the conversation! As I increase my knowledge about historical homes and buildings, you provided some valuable definitions and applications.  Most interesting to me was the use of the wall cavity as a drainage plane.

    • SLS Construction

      My pleasure & dittos to you.

      The drainage plane is one of the main reasons why Michael Anschell & many others start cringing when we hear people say they are just going to blow in cellulose or maybe use a slow rise foam in those cavities, and our first thought / statement is to make sure there is no water issues. Many of these older houses have survived as long as they have because of their ability to quickly dry out quickly because of the air space behind the sheathing.

      Now on the flip side, this might not be an issue on all houses (thus the check for…), even those where there is no sheathing, felt, etc… The one pictured above had a material similar to sheep wool blown in those cavities at some unknown date & was pristine when we opened up the walls. The catch was when was it installed – years before the vinyl siding was installed or just before. From everything we could determine it was done back in the 70’s which was well before the vinyl siding was installed.

  • johndpoole


    Thanks for keeping this conversation rolling with your own thoughts and impressions. Nice write-up. It sparks quite a few additional thoughts and reactions on my part, so I will attempt to communicate those here:

    First, I think you put the whole topic in good perspective by tying it back simultaneously to both the IECC, and the NPS guidelines. Many folks who have gone out on a limb to define what “DER” means often do qualify it in terms of “some percentage over a comparable building conforming to current energy codes”, which might, in some cases, make it all that much more challenging for an older building (e.g., you’ve got to go all the way out to 90% over actual building performance to hit 30% over a comparable, modern building’s performance; but then again, in the case of an old building, it’s often easy to achieve some large successes early on, followed by much detailed, fine tuning).

    You also provide an important reminder that ultimately this work is being done for the home or building owner and needs to meet their objectives. And I’d agree that many preservation folks pontificate on the merits of the procedures being used to achieve those goals, while somewhat losing sight of who controls the purse strings, and who really owns the project. But I think the reason why the historical preservation folks get so torqued over this is because of a perception on their part, which I believe is often correct, that many homeowners aren’t always aware of what treatments might be good or bad for a very old or historic home, or what their options or decision points are, or what preferable options might consist of.

    This is probably an unfair and grossly out-of-scale simplification, but in some way, DERs are being advocated for very old and historic structures in a manner not all that dissimilar from the way vinyl replacement windows were over the last few decades. The salesman shows up and says “I see you have a few horribly deteriorated wood windows, and most of the rest are painted shut. We can fix all that in one day, plus solve all your energy efficiency problems by 50% by replacing them all with new vinyl ones.” The owner signs the contract, hands the salesman a big check, all the windows get replaced (when only two or three actually needed replacing; the rest simply needed maintenance), and ten years later, seals are opening, meeting rails no longer meet and cannot be locked, and sash lifts are breaking off in the owner’s hand (exactly what’s happening today in my mom’s house, in fact). Meanwhile, colleagues of mine in the Windows Preservation Standards Collaborative (which I’m a part of, but don’t have the kind of time I wish I had to participate) have done extensive energy testing on older wood windows and found that, with reasonable maintenance, weatherstripping, and storms, the old windows they tested exceeded IECC 2012 requirements, at not nearly the cost of disposable vinyl windows. (The bulk of these results are supposed to be published about two months from now).

    Again, that was probably not a fair comparison, since, as you pointed out, a DER is far more than a simple, repetitive removal/re-installation project, but I hope this comparison at least helps others out there to better understand the preservationist’s mindset to some extent: our general concern is that many homeowners and many contractors don’t always have the full story on alternatives, and that there are strong advocates out there pushing for just one way of doing things. This is why I get so bent out of shape when Peter Troast says that designating historic homes as “hands-off” from DERs “condemns them to hospice.” No one in the preservation community is opposed to extreme energy reductions; no one wants to condemn older homes. We just think there are better methods than what’s often promulgated, or included in the popular definition of what a DER is.

    Your criticisms regarding in-kind replacement (use of same materials), and reversible treatments, I completely understand, but don’t totally agree with. Here are my counter arguments:

    There’s an active market these days in salvaged and reclaimed materials, which, for better or for worse, exists precisely because of all the tear-downs and replacements going on. Granted, reclaimed materials are not always convenient to obtain, but in the case of precise repairs for very old homes, I for one, always insist on going this route. Were I doing a Dutchman repair on an old wooden sash, for example, I wouldn’t in a million years opt for “white wood” (wet wood?) from my local Home Depot. Rather, I’d go to the trouble to acquire some old growth wood of the same species for that repair, so the repair would be that much more durable and weather resistant. Common wisdom seems to say, however, that since old growth wood is no longer obtainable, skip the repair and just replace the entire window with a vinyl “replica” that might, as a whole, last 1/4 as long as a properly done Dutchman.

    Now here’s another, more personal example: Before I acquired the Mansfield house, a number of clapboards at one gable were deteriorated and in need of repair or replacing. But the remaining siding was generally OK. Had I owned the house back then, I would’ve repaired bad areas with architectural epoxy, if possible, or would’ve replaced any un-salvageable boards using reclaimed old growth wood (even if that meant completely ripping and shaping new boards). But the contractor who was doing the roof at the time bundled in an offer to repair the gable siding along with the roofing job, which the previous owners agreed to, without even discussing with him how he’d approach it. What do you think he did? Well, he replaced ALL of the old growth gable siding with Home Depot -grade wet wood, of course!  So none of the durable, denser, old growth siding remains on that gable. For want of a few damaged old-growth boards, the entire gable exterior was replaced with inferior wood. And no one involved at the time — neither the owner, nor the contractor — even considered that fact. (Sounds a lot like the replacement window scenario I described earlier, doesn’t it?). This is what I mean by the stark differences in mindset about what’s acceptable when working on older properties, and why those folks who are preoccupied with preservation can get so worked up about what treatments are largely viewed as being acceptable.

    Regarding treatments that are reversible (sometimes called “re-treatable”), this is not held as an “always-must-have” goal for all work, but is one of many considerations weighed-in with other criteria, frequently as part of a decision making process or overall planning of work. No preservationist who knows anything would advocate blown-in cellulose or fiberglass in an old wall purely on the basis that it’s “reversible in principle” alone. Most understand that it really isn’t a reversible treatment, and furthermore, a durability risk if there’s water/moisture infiltration in the wall. But replacing a wall with a SIPS isn’t even reversible in principle.

    What might preservationists consider to be reversible energy-related enhancements to an historic property? Here are a few examples (these are just broad illustrations on my part, not necessarily complete or accurate specifications):

    1) Restoring and weatherizing old windows and air-sealing their perimeters, certainly. Conventional wisdom, and the way most DERs are performed, often call for complete replacement of existing windows. Yet my friends have demonstrated that old windows can be made to exceed IECC 2012 requirements.

    2) Insulating an attic floor by air-sealing penetrations, installing an air barrier, and filling the joist bays with rockwool batts, which have an R-value that slightly exceeds that of fiberglass, are resistant to moisture, have low environmental impact in their manufacturing, don’t have the moisture, settling, or leveling or fluffing issues of blown-in insulation, and can be accurately scribed to fit around penetrations and irregularly-shaped joists (in the case of really old timber frame homes). Maybe top it all off with a foam board on top of the rafters and under the floorboards to reduce thermal transfer by the rafters. (And, of course, the attic needs to be positively ventilated). But current DER philosophy usually says the only effective way to insulate here is to encapsulate the rafter system in spray-foam, or replace the original roof with SIPS.

    3) Air-seal an old wet-laid foundation wall or chimney column by re-pointing it with the same mortar that was originally used to bind it. (What a novel concept! Few folks remember these days that lost art called masonry). Insulate the interior foundation wall with rockwool (again, because of its R-value and moisture resistance). You’d have to build-in a stud wall to hold the rockwool in place, of course, and although not easily reversible, you could still un-do it at some time in the future, if needed. Contemporary DER philosophy says to completely encapsulate the wall or an unused chimney column in spray foam, making historical details no longer accessible to future historians.

    4) Some friends of mine at Historic New England needed to air seal and insulate the top of an old chase. They did so by employing a little creativity. They used tape and Tyvek to construct a “pillow” and loaded it with fill insulation (I forgot exactly what they used for the fill). With some effort and trial and error, they finally managed to get the pillow to fit the top of the chase perfectly and snugly. They had both a reasonable air seal and a thermal barrier in one fell swoop…a reversible treatment achieved using modern materials. Conventional thinking would’ve called for wood or sheet metal work, followed by caulking and/or spray foam.

    Anyway, sorry to be so long winded, but this is a topic I can’t easily put to rest. What I strive to do here, more than anything else, is to get energy and DER advocates to understand why preservationists object to the methods and materials of DERs as they are currently being promoted; that they have good reason to object to present day strategies for implementing DERs, the same way they have good reason to object to wide-scale window replacement with disposable/non-maintainable manufactured replacements.

    I think that divorcing the definition of “DER” from any particular implementation strategy would go a long way toward getting preservationists more comfortable with the concept (I feel that the concept itself is valid, and quite frankly, am a proponent of it myself, just not a fan of how many folks are currently promoting it). Also, I believe that empirically demonstrating that (mostly) reversible treatments, based on more traditional work methods, would also go a long way in this regard. Unfortunately, progress in that area is slow going, but it’s getting there. Hopefully, the pace will pick up as more results and methods get written about and published, and a certain amount of critical mass and mindshare begins to build. I personally hope that this conversation of ours will ultimately contribute significantly to the building of that mindshare.


    • SLS Construction

      You know, I would have gladly let you post that as a guest article… As for Allison’s brevity comment – sometimes life isn’t so simple. Fortunately I have an email of your reply to make commenting easy…
      You know it just hit me (as I delete my original 500+ word reply, maybe Allison will smile now) – in many respects you consider all DER’s as the same – i.e. if it looks like a nail it must be a nail. You seem them all as spray foam rigs whereas most I see & read about our cellulose & foam panels

      In some regards, I see your comments almost the same way as many other preservationists as you are missing one key point – what makes something historic. That was one reason why I framed my question to you on your article (I think it was there) on if you saw different methods based on the age requiring different methods.

      I fully agree that by breaking this down to areas or components might be the best, because while a DER might be an overall concept or system, it is made up of numerous components. I might also point out that not all of us have the time, budget or even availability to source old components.

      BTW, it was a SIS panel not a SIPS (1/2″ thick), and I like how you dodged my foam argument… ; )

      • johndpoole


        In your text, you wrote, and I quote you directly:  “…possibly a SIS (Structurally Insulated Panel)…”.  Structurally Insulated Panel — actually “Structural Insulated Panel” — is abbreviated SIPS, as in Since you wrote “Structurally Insulated Panel” I assumed that’s what you meant, and that’s what registered in my brain from that point on.

        But OK. You meant “Structural Insulated Sheathing” (I think) (like Dow’s styrofoam sheathing product). Now, it makes better sense to me why you contrasted it with 4″ foam. So I’m sorry if I took your writing of “Structurally Insulated Panel” too literally.

        On the other hand, I’m not exactly sure how I dodged your foam argument. If you’re saying that there are DER guys who see 4″ or 6″ extruded foam as the only possible solution (whereas you can otherwise achieve a nearly R30 wall with 2″ SIS panels and closed-cell foam — and I certainly don’t doubt the veracity of your argument), and that the DER guys are therefore equally guilty of seeing just one nail, just as the preservation guys often are, then I fully agree with you. 

        But I’m not sure how you might’ve expected me to respond to it. Because, in the case of either solution, you’re still talking about a retrofitting process whereby original materials and traditional workmanship are replaced, often to some considerable extent, with synthetics. And this, in and of itself, is precisely what so many preservation guys object to, because it seems contrary to certain values they subscribe to (whether you agree with those values as a starting point, or not). So yeah, you’re right; these techniques do indeed begin to all look like the same nail to someone imbued with a traditionalist/ preservationist mindset. But there are certain reasons for that being the case, and that’s what I was trying to point out and illustrate, as best I could.

        Anyway, I haven’t read your email yet, but will do so now. Maybe that will give me some better understanding of your criticisms of my response. Not sure if I’ll have time to respond tonight, but most likely by sometime tomorrow.

        ~ John

        • SLS Construction

          Busted & I see why you got SIPS now – you are right it was supposed to read sheathing & not panel – thanks & I did correct it above

          As for the dodge – I was reading / seeing was when you said no preservationist would recommend Cellulose or FG just because… but nothing on the foam being used in the cavity.

          Hopefully the email doesn’t confuse the subject to much more as they were thoughts based on each paragraph & then the following above thought popped in my head (for better or worse) 

          I have no problems with the base principles, but to often it seems like the words “specific rehabilitations” has turned into all rehabilitations & reasonable means reasonable to X view, not what is best for the long term health of the property and to a slightly less extent best for the occupant / owner /steward.

          No worries on responding tonight as I got another novel I have to finish off… In all seriousness I look forward to the reply & seeing others thoughts on it to – Thanks again bud

          • johndpoole

            Ah, OK. I see how you meant that now. No, it wasn’t an intentional dodge; I just didn’t consider it while I was busily typing my earlier comment.

            I replied to your email, and all good. One thought that occurred to me is that it might be helpful if we came up with a taxonomy of the common strategies used in DERs. I fully agree with you that every project is unique and that they all might have differing goals. But presumably, enough have been completed and written about so that some attempt at classification might be possible. I don’t know…it’s just a thought. Let me know if you agree.

            Hope you’re having a good one, too. And converse with you again soon….


      • energycircle

        Sean and John P:

        I don’t think it’s been said clearly enough throughout this discussion that DER does not automatically equate to external insulation. I like Linda Wigington’s Thousand Home Challenge definition of 70-90% of annual site energy consumption. Operational not just modeled. Get there any way you can–wool hats and solar panels included. She’s steering away from DER as referring to retrofits and shifting the R to reductions.

        For sure, getting to Deep, especially in northern climates, will entail some envelope work, but I think it’s in everyone’s interest to break the assumption that DER always = exterior envelope. 

        Reading through all that’s been written here, I’m also struck by the presumption that DER’s of historic buildings is somehow rampant and growing. I wish this were the case, but I’m afraid the real number of historically valuable buildings being considered for DER is tiny. Personally, I want to see the DER concept grow substantially, because any real solution to existing housing stock demands it. That’s why I’m engaged in this topic. But right now the concept is on the periphery at best. 

        Perhaps I’m as guilty as anyone for fanning the flames of a controversy that may not really exist in the real world. But, as I’ve said, the uniformity of the preservationist opposition is what irks me. DER’s are a good and important concept, but a fledgling one that needs positive support. 

        • SLS Construction

          I definitely agree we need to break that assumption that DER always equals X, as it varies on the parties involved and that house.
          I don’t think we are saying it is rampant, but rather trying to help others understand what is involved & how they can get this work done without just throwing up their arms thinking that they are stuck.
          Oh no, the controversy exists and as Allison pointed out in his article, it applies to projects other than just DER’S.
          Getting back to the first paragraph & Linda Wigington – I think that will probably be a future article & looking at the tweet up between the two Johns last night I expect to see more on just the definitions soon.  

          • energycircle

            No doubt that the definition is an issue. The industry is all over the map.

  • Jeremy Laurence

    This is a great post with interesting comments, I really enjoyed reading it. I must say that the subject matter is well discussed and I will definitely coming back for more. I’m gonna bookmark and share this to my friends. Thank you for this!

    • SLS Construction

      Thanks for stopping in, leaving a comment & sharing with others – I think I can say on behalf of the others that it is much appreciated. One item I would like to mention, is if you or someone else has something to add – please feel free to chime in. The more people participating, the better

      Thanks again