Planning to change siding
Martin et al,
I have decided to re-side my house, because the many-layered paint on the cedar clapboards is peeling and I don’t want to strip and paint it, or pay $12,000 to have someone else do it.
I am a very experienced DIYer, but not a pro, so I thought I’d outline my plan to see if anyone has red flags to raise.
It’s a 1940 cape-and-a-half in Western Massachusetts. I would love to wrap it in rigid foam, but it’s maybe a five to 10-year house for us and the extra cost, plus trim complications, potential tightness issues, etc., scare me off.
So my compromise route: strip off the clapboards and brittle old building paper, and install pre-painted Hardieplank (because I hate painting) on top of a “rainscreen” housewrap such as Hydrogap. The sheathing is diagonal boards. I have thought about using furring strips over 30 pound felt (I have experience working with it I like its ability to absorb moisture from the sheathing), but the textured housewrap just seems so much easier because I wouldn’t have to fuss with the trim.
Does that plan seem sensible enough? Does anyone want to suggest I should:
Consider a different house wrap for whatever reason?
Reconsider a real ¼” furring-strip rainscreen?
Reconsider adding insulation, like at least have the walls dense packed with cellulose while the siding is off? (Even that would be several thousand dollars, right?)
Consider other siding options? (We do not like the aesthetics of vinyl, and as I mentioned, I don’t want to paint.)
Having done a lot of reading and listening about building science, it sort of kills me not to take this opportunity to make the house much more efficient, but it seems like it would quickly become a $20,000 job rather than a $7,000 job.
Any thoughts much appreciated.
Alex
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Replies
What is in the wall cavities?
You might consider Benjamin Obdyke Slicker as a middle ground between the BO HydroGap and wood furring strips.
Thank you Brendan, will absolutely check it out.
Good question Dana: very old fiberglass batts in almost all cavities (some appear to be uninsulated per prior energy audits, perhaps because they contain old ducts no longer in use, if I recall correctly). The fiberglass does something, but how much, I don’t really know. House seems to me like more of an energy hog than it should be.
When the siding is off it's an opportunity moment to add insulation to under insulated or uninsulated stud bays. It may or may not be possible to yank the old batts out easily, but even if one has to drill a couple holes per bay, blowing insulation into the bays and packing out over the old batts will fill the exfiltration paths with air-retardent fiber, and will eliminate any gaps. This reduces air infiltration and bypass paths (including filling in some of the seam of the planks) and it's not really all that expensive, cheaper still when performed during a re-siding project, when there isn't any cosmetic cleanup/repair of siding or wallboard to be done.
It's also an opportunity moment for air sealing, and rectifying any deficiencies in the window flashing. Plank sheathed houses are notoriouly air leaky. For air sealing plank sheathed buildings a fully adhered WRB such as Blueskin VP 100 will tighten up the place a LOT better than detailing a broadsheet housewrap such as HydroGap as an air barrier. It's not cheap stuff- almost twice the price of HydroGap but with plank sheathing it's the best bet for air sealing the sheathing plane. Think of it as 4 foot wide strips of vapor permeable airsealing tape, that can also be used as flashing tape.
To establish a rainscreen gap, cut 1.5- 2.5" wide strips of 1/4" fan-fold XPS and staple them up over each stud after the fully adhered WRB goes up. If you use perforated fan-fold (eg GreenGuard S14) the perforations are on an appropriate width grid to make eyeballing the cut easy.
Doing both the remedial insulation and fully adhered WRB is "worth it", even if you're moving in 5-10 years. You'll reap the benefits in creature comfort and lower energy bills, even if it may not pay off completely on energy savings alone. The Baker administration and others keep pushing the "home energy efficiency scorecard" to be assessed and divulged prior to sale, which will eventually find it's way into a state energy bill, at which point having the better insulated tighter house may make it easier to sell and at a higher prices.
https://energynews.us/2019/04/02/northeast/massachusetts-bill-would-require-home-energy-efficiency-scorecard-before-sales/
Hi Alexander -
The HydroGap can be detailed to be some level of exterior air control layer along with functioning as a weather-resistive barrier so that seems like a pretty good choice for your situation.
Just be sure to use a high performance acrylic pressure-sensitive adhesive (PSA) tape at all margins and overlaps of the HydroGap and weather lap as best you can at penetrations.
Check out the Benjamin Obdyke website for blogs on how their products get used in renovation, such as this one: http://www.benjaminobdyke.com/jobsite-gallery/projects/hydrogap-installation-by-camenish-company/
Peter
With a diagonal ship lap sheathing the efficacy and quality of HydroGap as the air barrier is highly questionable. See my comments in response #9.
That’s excellent, thanks Peter.
If you’ll have the walls open from the outside, that’s a good time to replace old, deteriorated fiberglass batts. I’m a big fan of mineral wool batts for this application.
Bill
Thanks Bill. It seems labor intensive to take off sheathing but maybe it wouldn’t be so bad.
Get a GOOD nail puller, a mini sledge, and a small prybar. Then go to town on the old sheathing. It’s time consuming but not too bad to remove. Once you have the walls open, you can remove the old insulation, and you can air seal all the gaps and holes you find as well as any electrical boxes. Put in new insulation and close things up and you’ll have a MUCH better sealed wall assembly. If you are having comfort issues and you’re doing a reside, it’s really worth addressing the insulation and air sealing issues at the same time.
If you are going to try removing the structural sheathing, don’t do it all at once — leave some boards up as you go. If you remove too much at once you can have structural issues. I noticed you have plank sheathing and not plywood, so you probably don’t need to remove every board to be able to get enough access to the wall to do the insulating and air sealing work. Just remove enough to open up gaps big enough to do the work while leaving the rest in place to brace the structure.
I’d strongly recommend trying to get some rigid foam up too if at all possible. A reside project is the only time you really have the option to add exterior rigid foam and it really improves the insulating value for the walls.
Bill
Don't bother stripping the sheathing!
If the nails are in good enough shape that dense packing won't pop them loose you can dense pack fiberglass over the existing batts to get the equivalent or better performance than rock wool batts. Even at a lower mid-density an over-blow of fiberglass or cellulose would fill the voids and fit better than even the fussiest of batt installers could achieve.
If the wood and nails are ok, I’d try dense pack too. A layer of rigid foam over the wall detailed well would take care of the air sealing with a lot less overall work.
Bill
Thank you guys. Are you saying I can fill the cavities with cellulose with a rented machine and do a decent enough job to make a difference? I was under the impression those were only good enough for loose fill on the attic floor and such. Or are you suggesting hiring a professional to sense pack?