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Skylight leak? No, probably not.

I'm convinced that most moisture issues with skylights are condensation issues that are misdiagnosed as leaks. To start with, skylights are notorious for leaks among roofers. I've heard roofers say "There are two types of skylights: those that leak, and those that are going to leak." I think they're usually referring to the old bubble-type skylights like the one pictured below. How could that thing possibly not leak?

Bubble-type Skylight

I don't feel the same way about other modern skylights, however. In all of my years of inspecting, I've only found a few skylights that leaked, and they were inferior products that were poorly installed, such as the one pictured above.

On the other hand, I've found hundreds of skylights with condensation problems. These show up as black stains on the roof sheathing in the attic, and as stained drywall on the finished side of the skylight shaft.

Stained skylight shaft

stain at top corner of skylight shaft

Wet skylight shaft

I've even found skylight shafts that were completely void of insulation:

Missing insulation at skylight shaft

These are not skylight issues; these are skylight insulation issues. This is a detail that is almost never done in a manner that will perform well, despite the fact that proper insulation methods have been known for a long time.

Fiberglass should be encapsulated

When fiberglass batts are used to insulate around a skylight shaft, the insulation should be in contact with a surface on all six sides. This is where it goes wrong. In most cases, the fiberglass batts are open to the attic side, which allows for air movement and excessive energy loss. This is what causes condensation on the house side of the skylight shaft.

For a nice diagram showing how to properly insulate a skylight shaft the old-school way, check out this diagram from the U.S. Department of Energy:

Skylight shaft insulation diagram

The often-missed detail in that diagram is the sheathing on the attic side of the skylight shaft. The best material to use as sheathing is rigid foam insulation. Not only is it light and easy to work with, but it will help to increase the insulation value of the shaft.

The U.S. Department of Energy has several more illustrations and photos on their website, all discussing the importance of proper insulation around skylight shafts. The image below gives a nice example of what a properly insulated skylight shaft looks like:

Proper skylight shaft insulation

I've probably seen a handful of skylight shafts that looked like that, but no more. This is a rare bird. Here's an attempt that comes close, but there was no air sealing performed.

rigid foam around skylight shaft

As I said, however, this is the old-school way of doing things.

New-school method: spray foam

The new way to insulate skylight shafts is to simply spray-foam the whole thing. This is far less labor-intensive, and there's a lot less that can go wrong. The photos below are courtesy of the fine folks at Atticus Insulation (greatest name ever).

Spray foam at skylight shaft 1

Spray foam at skylight shaft 2

Spray foam at skylight shaft 3

Spray foam at skylight shafts

A poorly insulated skylight shaft means an increased potential for condensation problems. Additionally, this increases the potential for ice dams because of the excessive heat loss that occurs around the skylight shaft. To have this detail corrected, the best option is to work with a good insulation contractor to have the whole thing spray-foamed. I chatted about this topic with two insulation contractors here in the Twin Cities who both do excellent work. One of them was Atticus Insulation, and the other was Houle Insulation. Neither one of them would do anything but spray-foam a skylight shaft. Amen to that.

Author: Reuben SaltzmanStructure Tech Home Inspections

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Bonding gas piping

When it comes to people, 'potential' is a good thing. When it comes to gas piping, not so much. Specifically, electrical potential. In fact, that applies to all metal piping systems inside a home. Anytime there is electrical potential between different systems, there's a possibility for shock, fire, damage to equipment or electrocution. All bad stuff. To help mitigate the potential for potential, electricians bond stuff.

To make it really simple, when metal that can carry electricity (but shouldn't) gets connected together to eliminate potential, we call it bonding. If the metal accidentally carries electricity or even a static charge, proper bonding will allow the electricity to be carried back to its source in a safe manner. Oftentimes, there will be so much current that it trips a circuit breaker.

Old-school bonding for gas piping

Way back in time before we had all of this new-fangled gas equipment like forced air furnaces, the gas-fired equipment in our homes was simply gas-fired equipment. Electricity didn't play a role, just like electricity still doesn't play a role for natural-draft water heaters. Our gas appliances were operated by gas alone. To help make sure that everything stayed at the same potential, it was common for gas and electrical systems to be bonded together with a big piece of copper wire and a couple of bonding clamps. It would look something like the photos below:

Gas and water bonded

Gas and electrical bonded

Gas and water bonded

According to electrical guru Douglas Hansen, gas suppliers started getting whipped up about this, saying they didn't want electricity on their pipes. Of course, that's not what a bonding wire does, but some men you just can't reach. So you get what we had here last week I have pictured below; there used to be a bonding wire connected to those clamps, but someone removed it.

Bonding strap removed

This would be a concern on a very old house with very old gas equipment, but it's not an issue with newer homes.

Modern bonding for gas piping

Today's bonding requirement for gas piping comes from section 250.104(B) of the 2017 National Electric Code (NEC), which says the following:

If installed in or attached to a building or structure, a metal piping system(s), including gas piping, that is likely to become energized shall be bonded to any of the following:

(1) Equipment grounding conductor for the circuit that is likely to energize the piping system

(2) Service equipment enclosure

(3) Grounded conductor at the service

(4) Grounding electrode conductor, if of sufficient size

(5) One or more grounding electrodes used, if the grounding electrode conductor or bonding jumper to the grounding electrode is of sufficient size

The bonding conductor(s) or jumper(s) shall be sized in accordance with Table 250.122, and equipment grounding conductors shall be sized in accordance with Table 250.122 using the rating of the circuit that is likely to energize the piping system(s). The point of attachment of the bonding jumper(s) shall be accessible.

In most cases, option #1 is used, and it happens automatically at the appliance. For example, if a forced-air furnace is properly installed, then the gas piping that runs to the furnace will also be properly bonded at the furnace. The images below show how this works:

Gas piping bonded at furnace

Pretty simple, huh?

I've heard from home inspectors in other parts of the country that this kind of bonding doesn't cut it with the municipal inspectors, however. In those cases, another step must be taken, which involves separate bonding for the gas piping, as shown in the photo below.

Extra bonding at gas piping

This image is courtesy of Seattle home inspector Charles Buell. I've never seen anything like this here in Minnesota unless it's on CSST.

This doesn't apply to CSST

Corrugated Stainless Steel Tubing, or CSST, is a different animal. The basic requirements of the NEC still apply, but CSST manufacturers have their own requirements, as does the National Fuel Gas Code (NFGC). Check out my blog post from last year for more info on that topic: CSST Bonding

https://structuretech1.com/csst-bonding-requirements-final-update/

Author: Reuben SaltzmanStructure Tech Home Inspections

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