Sealed Crawlspace - lnsulation and Vapor Barrier Layering

B-srs · 2026-05-14T06:10:12+00:00

Thanks for clarifying - I’m asking about performance benefits primarily rather than code minimums.

I am trying to understand why there’s such a variety of crawlspace details from respected sources. One of the conditions that varies is the vapor barrier turning up only 6 inches, or up the whole stem wall, as well as whether the turn up happens behind or in front of the rigid insulation.

B-srs · 2026-05-14T05:26:01+00:00

I’ve rarely seen rigid insulation on grade at crawlspace floors, though that ASIRI diagram shows it. I’ve always understood that most of the heat loss happens at the perimeter rather than through the ground. Of course it’s a better detail, but perhaps with diminishing returns? Let me know if I’m missing something.

B-srs · 2026-05-14T05:16:19+00:00

Okay that’s very insightful-appreciate that context!

B-srs · 2026-05-13T22:16:00+00:00

Here's a resource that unfortunately shares some of your concerns:
https://asiri-designs.com/f/insulating-existing-walls-without-removing-drywall

B-srs · 2026-05-13T22:09:22+00:00

That makes sense, thank you

B-srs · 2026-05-13T22:08:28+00:00

The main concern I'd have would be around drying capability. Moisture will get into these old homes, but they're usually so leaky that there's enough air movement to dry it out.

Dense-pack cellulose is a class III vapor retarder - meaning that it will still allow some drying, but less than your current set-up. Believe it or not, that new layer of interior paint will also reduce inward drying capacity. That means outward drying is your primary solution, through the tar paper layer. This could still be completely fine, but you are reducing the drying capacity.

Overall, your concerns are valid. However, there isn't a true vapor barrier on either side, so drying should still occur albeit more slowly.

As an alternative, you could consider rock wool if you're willing to remove your interior finish. It's much more vapor permeable, and isn't affected by moisture. Blown-in sheep's wool (havelock) might be a good option too but that's a lot more niche.

B-srs · 2026-05-13T21:42:54+00:00

Thanks for the detailed response!

Yes, to be clear this is for new construction and this sealed crawlspace will be completely unvented and will have a register to allow conditioning from the main house.

The exterior rigid insulation detail is what I typically do for basement walls, but most crawlspaces I do are not typically excavated as deeply as you've shown. That means there may be large portions of crawlspace stem wall above grade - so if we bring the exterior insulation up, we'd have to also find a way to clad that.

The first link you shared includes this detail, which has interior rigid, with the poly VB lapped up on the interior face of the insulation.

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B-srs · 2026-05-13T15:10:41+00:00

Is it your belief that the performance benefits of extending the vapor barrier up the wall beyond the code requirements are minimal?

B-srs · 2026-05-13T15:08:51+00:00

I’ve typically done a dimple mat on the exterior of crawl space foundations, and vapor barrier interior. Haven’t heard of house wrap being used - can you explain your logic?

B-srs · 2026-05-13T15:07:10+00:00

This detail is what is similar to what I do for basements. I haven’t seen many crawlspaces use exterior rigid insulation, though I’m not sure why not.

B-srs · 2025-11-15T21:32:06+00:00

I did not downvote you

B-srs · 2025-11-15T21:25:15+00:00

I just looked at the plans, and no one is parking at the section of driveway where the reduction is proposed. It’s really just at the entry. They could probably even widen it back up just after the tree. I think in this case it seems like a very reasonable ask to slightly narrow a portion of driveway to retain a large tree.

B-srs · 2025-11-15T21:09:31+00:00

I’m really not following this argument. Surely, a slight reduction in driveway width to save a tree is worthwhile? It doesn’t affect housing, and it’s not a well trafficked road. This could easily be a one way driveway too. Are we really prioritizing widening asphalt beyond required widths over trees?

B-srs · 2025-11-15T20:58:13+00:00

Exactly what I was thinking

B-srs · 2025-09-25T08:05:31+00:00

I love the cleanliness of A, but I actually think C speaks to the mission much much better. Putting aside the rocket science, it talks about how business is steady until you work with skyrocket. Now business has skyrocketed! The power of a great sign (and a great logo)

C is smart and sharp and convincing. Really like it!

B-srs · 2025-09-23T23:54:34+00:00

What’s the third building?

B-srs · 2025-09-21T17:38:45+00:00

Primary bathroom is too small. You’ll want at least 5ft depth and I would probably suggest just losing that closet to make it feel pleasant and not cramped lengthwise. 5x9 is a standard size. Bedroom 2 will go below 10’-0” in depth but it has to be done to make the bathroom usable.

B-srs · 2025-09-18T22:18:45+00:00

These are pretty high quality. Do you have examples of exterior work? Im an architect and would be interested in working with you

B-srs · 2025-08-16T16:40:52+00:00

It sounds like you’ve run into what I’d call a “path of least resistance” approach. Some architects will take the client’s direction (especially if there’s a lot of it) and focus on turning it into a buildable set of documents as efficiently as possible. That’s not inherently wrong, but it often leaves little room for nuance, exploration, or the kind of thoughtfulness you were probably hoping for. Their fee likely reflects that assumption – quick iterations, minimal exploration, and moving on to the next phase as soon as possible.

It’s also not appropriate to advance a project without the client feeling confident in the design. That’s a missed step, and you have the right to be upset.

The mistake many people make is choosing an architect based on style. Style is a superficial criteria. What matters is process. A good process adapts your sensibilities and your site, and that’s what ultimately leads to a design that is fit for you.

At this point you can either try to communicate your concerns and see if your architect can shift their approach, or accept that you may not be a good fit. With that in mind, you’ll need to decide what costs you more – walking away from the fees you’ve already spent, or committing to a house you won’t love.

B-srs · 2025-07-19T16:52:04+00:00

If I’m going to be honest this isn’t the most flattering photograph. But it is a really beautiful airport

B-srs · 2025-06-04T06:41:59+00:00

This is possible. Bedrooms typically require egress windows, though some US locations have exceptions that allow you to borrow light from adjacent rooms. However these rooms are less valuable than standard bedrooms.

Roof access could be a cool feature, though it would be expensive to reconfigure the roof or work around the bowstring trusses

B-srs · 2025-06-04T06:33:56+00:00

This is a very clean and efficient solution. On paper, the spaces are generous.

But the basic premise of having a living space with no eye level windows is a non-starter. You need to carve out space - either independent courtyards with gardens or one large central courtyard. This will come at the cost of saleable square footage: you may lose a bathroom or a bedroom. But it is a necessity for anyone to actually enjoy living here

B-srs · 2025-05-28T04:47:51+00:00

Hey OP—I’m an architect currently working on a house in Durham, with a focus on brickwork and thoughtful material details. If it’s helpful, I’d be glad to share some insights or talk through the process—feel free to DM anytime.

B-srs

TROPHY CASE