Green Building Advisor

| Posted in Energy Efficiency and Durability on July 19, 2026 07:25pm I am looking for some advice on how to better calculate the size of an HAVC system for use in a 4500 SIP home. The home is a combination ICF for foundation walls/basement of 1800 sq ft, then SIP walls/roof with an R40 for the main floor also 1800 sq ft. there are two small bedrooms on the second floor which adds another 900 sq ft.

I’m building a tiny house on wheels (8.5’ x 30’ trailer) and I have a very basic question about using a site-built “SIP” (plywood> 3-4’’ rigid foam > plywood) to thermally isolate my trailer frame metal from the wood floor and walls. I’m interested in the site-built SIP approach for adding a layer of insulating material between the trailer metal and wooden structure to prevent moisture/condensation problems.

Hello, I’m looking for WRB advice. Repairing or totally replacing siding. I’ve been reading old articles/Q&A, but I apologize if I’ve missed available info or have failed to grasp basic concepts. 1987 MN home, zone 6a. Wall assembly is drywall, interior poly, 2×6, insulation batts, bildrite asphalt board, and masonite. WRB selection worries me due to due to wall’s inability to dry inward.

Editor’s note: We first published this article in 2025 when wildfire smoke from Canada blanketed large portions of the United States. Because the information remains relevant—and, unfortunately, timely as poor air quality once again affects much of North America—we’re republishing it with minor edits and updates. I’m pretty much an indoor air quality (IAQ) nerd; I own four different indoor air-quality monitors plus a radon monitor and portable CO and CO2 monitors.

| Posted in General Questions on July 17, 2026 02:42am Hello, I’m building a new home in southeast Alaska zone 7. Ive got 3in of polyiso with taped seams on the outside with no interior vapor barrier. ventilation and humidity control will be very important. My crawl space will be a conditioned space with rigid insulation on the ground and vents in the floor. Ive got a few pioneer mini ERVs for fresh air. how important is the location of these units? i will have one upstairs and one downstairs.

Most builders spend their time reading the requirements in the building code. Few spend much time reading the definitions. Yet some of code’s most important language lives in Chapter 2. Defined terms often determine how an entire section should be interpreted. With every code development cycle, I become more aware of the importance of language in the building codes. My intent is often to make proposals more descriptive, leaving less room for interpretation by users and code officials.

I was working on balancing a system yesterday and ran into a situation where we couldn’t get the rated air flow out of the system. Long story short, I ended up calling Mitsubishi tech support and chatting with them. I told them we were only getting 530 cfm out of a system rated for 675 cfm. Our total static is .3 in. WC, and supply side is .13 in. WC. The support rep told me that my duct work was too big.

Over the past few years as a designer and construction coach, I’ve had the privilege of helping homeowners navigate the complex path to net-zero. In this three-part series, I’ll introduce you to my latest clients and the slice of paradise they found in rural Wauzeka, Wisconsin (climate zone 5A).

I’ve posted before about the fire smoke filtration system I’ve been working with for about 3 years now. It’s based around an 8” AC Infinity (refillable) carbon canister, and a 16x24x5” MERV16 filter. As I write this PM2.5 outside in NW Ontario is 113 ug/m3 due to dense fire smoke. Inside, we’re at 5 ug/m3 while the HRV runs at 75CFM. Video is 1 minute long: https://youtube.com/shorts/m5MNmqSAIf8?si=Mo_cor0yIPIp4_c1 I hope it proves useful.

| Posted in General Questions on July 15, 2026 03:20pm Hey all. Seeing if anyone has slick ideas on how to air seal simple attic access. I have a few ideas but trying not to reinvent the wheel. Photo attached. Thanks. A collection of one thousand construction details organized by climate and house part Search and download construction details Start free trial