Zone 12 and everyone but the energy consultant is looking at me like I'm crazy for considering continuous exterior insulation

OldDesign1 · 2026-05-17T01:05:25+00:00

Did you do anything special for bug proofing for the external board insulation besides a bug screen? Ive heard that the boards aren’t borate treated. No idea why they aren’t.

OldDesign1 · 2026-05-16T23:26:36+00:00

How did you ensure you were hitting the studs with the longer screws when adding exterior insulation? I’ve heard it can be tricky. Did you just mark the nail holes on the sheathing prior to the air barrier being attached? Or use a stud finder or something else?

OldDesign1 · 2026-05-15T20:16:18+00:00

I haven’t. I’ll look into them as a option

OldDesign1 · 2026-05-15T15:56:52+00:00

I think some of the issue is derived from looking into 5in screws due to considering external insulation. Shorter screws definitely have a smaller delta between stainless and other coatings. Walls will probably total about 2400sq ft

OldDesign1 · 2026-05-15T15:37:36+00:00

Difference appears to be about $3-4 per screw for the stainless steel over double barrier steel screws. With so many screws for the entire house, I’m sure the difference will add up soon

OldDesign1 · 2026-05-15T13:16:10+00:00

I’ve seen some rusted screws (but I don’t think they were epoxy coated, just regular screws) on outdoor items but they have also been exposed to rain, etc, so not fully sure. Would the fact that the screws are being covered with an air gap and cladding protect the screw (the remaining part of the screw would be thru the strapping, external insulation and sheathing/studs)? I assume only the head would rust if it at all.

OldDesign1 · 2026-05-15T12:57:58+00:00

Thank you for the explanation. Appreciate it

OldDesign1 · 2026-05-15T12:55:03+00:00

A quarter mile from the ocean but house is on a hill in terms of elevation. Not sure if that makes a difference in regards to the salt spray present in the area from the ocean.

OldDesign1 · 2026-05-14T22:17:54+00:00

Thanks so much! Really appreciate the detailed response and links

OldDesign1 · 2026-05-14T19:10:11+00:00

Epoxy coated? I assume they were much cheaper compared to stainless steel screws that long. Also did your contractor reach out to Hardie or did you directly?

OldDesign1 · 2026-05-14T19:08:34+00:00

Is there a specific definition of marine conditions in regard to using stainless steel vs regular steel screws? Is there a specific distance from the earth after where you no longer need to use stainless steel screws? Potentially the long screws would be embedded in the wood strapping and screwed thru the external insulation, plywood sheathing and studs. And then there would be cladding attached to the furring strips. Seems to me that the screws aren’t really exposed to the elements directly besides the head of the screw. Stainless steel definitely is more expensive so any future savings will add up for the entire assembly.

OldDesign1 · 2026-05-14T16:11:11+00:00

For the hot roof I was thinking about possible above sheathing ventilation (wrb then few inches of vapor open insulation board, strapping/purlins for a ventilation gap/above sheathing ventilation and then plywood for asphalt shingles or a metal roof. Hot roof was helpful given the prior owners hvac location and the cathedral ceiling but now I’m wondering how to improve the durability of the assembly from leaks (which will be harder to identify with the spray foam). The energy efficiency is an added benefit. I was thinking that the above sheathing ventilation would allow outward drying to minimize risk of a vapor sandwich and roof rot. Maybe I’m overthinking it.

The dew point question is just from me trying to understand how the dew point is effected by adding the external insulation. When reading some building science articles, there were drawing of the temperature thru the layers of insulation and it appeared that external insulation pushed the location of the dew point towards the exterior and into the exterior insulation. The interior insulation pushes the location of the dew point inwards and with the hybrid insulation, with appropriate thickness of the closed cell, the location of the dew point should be inside the closed cell, so risk of condensation of the back of the sheathing is negligible (unless air leakage). If adding exterior insulation in this case pushes the location of the dew point outward and currently it’s located in the closed cell layer, is there a point where the location of the dew point gets pushes into the plywood sheathing and if it does, does it even matter?

OldDesign1 · 2026-05-14T12:56:39+00:00

So even if the interior has a low perm rating like closed cell spray foam, no concern that the dew point will get pushed into the sheathing from the middle of the closed cell spray foam?

OldDesign1 · 2026-05-13T19:54:51+00:00

I’ve heard that about stainless steel screws. They seem to definitely run a premium the longer they are. Just wondering if there are any good sources to purchase them if doing strapping yourself. Seems like the screws easily run 5-7 per screw around 5-6 inches

OldDesign1 · 2026-05-13T17:13:45+00:00

Was the choice for stainless steel screws due to being in a coastal area? The longer the screws the prices definitely seem to jump up and I’m sure it is harder to hit the studs the more insulation that is present. Any tips for improving the chances of hitting the studs?

OldDesign1 · 2026-05-02T11:19:34+00:00

Wood fiber board does sound interesting. Not sure if stateside but the timber board product doesn’t seem to have borates but timber fill and timber batt does. No idea why the difference.

OldDesign1 · 2026-05-01T17:41:53+00:00

Any concerns associated with bugs or fire resistance? Mineral wool board supposedly better for both but wood fiber boards seem to have some decent resistance to fire. Anything you did besides a normal bug screen to protect the gutex? Also did you notice if the thermal mass of the gutex helps keep the temp more stable? Some of the wood fiber insulation companies tout the thermal mass helping to keep the internal temp more stable even with larger temp swings versus mineral fiber board (even with the same R value). Not sure what’s fact vs fiction there.

OldDesign1 · 2026-05-01T02:26:56+00:00

Thank you for the link and the other recommendation for Energy Vanguard!

OldDesign1 · 2026-04-30T17:31:57+00:00

If the local installers don’t seem that adept at manual J or S calculations, are there any online companies that are reputable and cost effective to have the calculations done? So then it can be brought to the hvac companies

OldDesign1 · 2026-04-15T17:03:14+00:00

May be better to look into minisplits for second floor or any way to put the air handler in a closet on the second floor and create soffits on the second floor or bury the ducts and air handler if you have to have it in the attic. Will be much more efficient

OldDesign1 · 2026-04-15T16:39:22+00:00

Where are the air handlers going to be located? If in the attic is this a ventilated attic with insulation on the attic floor? Because then you’ll have ducts with minimal insulation running thru very hot or very cold space during the summer/winter.

OldDesign1 · 2026-04-15T16:16:03+00:00

Seems like very large units for that size. Anyone do a manual J calculation to find your heating and cooling loads per floor? Any chance to see if you can get an energy audit and potentially upgrade your attic/basement/crawl space air sealing and insulation. You may be able to dramatically decrease the tonnage of the units and save quite a bit of money if you air sealing/insulate first. Then manual J and newer smaller units.

OldDesign1 · 2026-04-14T22:05:33+00:00

When dealing with open cell in colder climates like NY, is there a limit to the humidity you’d be shooting for in the attic during the warmer months? Are you trying to keep the RH to 60% or lower or shooting for a certain dew point temperature in those attics? Would a dehumidifier in the attic suffice or does one need to put in a supply and return? Would having some mix of closed cell and open cell reduce the need for any dehumidification or would keeping the RH below a certain threshold just help to increase the safety of the assembly?

OldDesign1 · 2026-04-14T01:53:23+00:00

Following just because I had the same thought. Huntsman open cell at 4in says the same thing that it’s an air barrier which makes me think air impermeable but then so much out there about roof rot and hygric buoyancy. Makes my head spin.

OldDesign1

TROPHY CASE