How to insulate an outdoor water line or under the roof
SPRAY FOAM UNDER A ROOF? Q Is it a good idea to use spray foam insulation directly on the underside of a roof, or does there need to be an air space and ventilation? I’m building a new woodworking shop and will be using spray foam on the walls. Should I use it up above, too?
A The short answer is: “Maybe.” If you’d like to have the attic space cool in summer and warm in winter, then yes. Spray foam applied under the roof sheathing and between the rafters is a great idea. This approach converts what’s normally wasted attic space into something useful for storing lumber, tools and supplies.
That said, you’ll need to frame your roof steeply enough so the roof is high enough to walk under.
Also, to get the most usable space, you’ll need to frame your roof with rafters, not trusses. No ventilation is needed when spray foam is used under a roof like this, but there is something to remember: Be sure to use fibreglass shingles for your roof, not the older style organic asphalt shingles. Organics break down from the hot surface of unventilated roofs in summer.
I’ve built two buildings with unventilated roofs insulated with spray foam and they work quite well. The tiny bedroom you see in the photo here is a case in point.
You get way more usable space for a small extra investment in materials.
If your roof will be shallow enough that you can’t walk under it, then ventilate the attic space to the outdoors and insulate the floor of the attic with batts in the usual way. This costs less than spray foam.
FREEZE-PROOFING A CABIN WATER LINE Q What’s the best way to freeze-proof a water line from a spring to a vacation cabin we visit year-round? There’s not enough soil to bury the pipe below frost and we don’t want to invest in anything fancy or expensive for keeping running water flowing.
A I’ve used a simple and economical approach with great results.
Start by feeding the water line inside a four-inch ABS drain pipe that runs from your cabin to the water source.
Every hardware store sells ABS pipe. It’s tough, economical and is easily sawed and joined. This black pipe protects the smaller water pipe inside it, and the air around the water pipe offers some insulation value.
Next, pull an electric heating cable through the ABS pipe alongside the water pipe.
In installations I have done, I connected the ABS pipe to a toilet flange in the floor of the building, with the water pipe and the heating cable coming up into the building through the flange.
The heating cable keeps the water pipe from freezing, but it doesn’t need to operate all the time. In fact, because of the insulation provided by the air around the water pipe, the heating cable only needs to operate for short periods of time. The warmer it is outdoors, the less heat the cable needs to deliver.
I’ve had perfect results controlling water line heating cable operation with a $60 device I bought called the Inkbird. It includes a probe that monitors the temperature inside the ABS pipe.
Adjust it to switch the heating cable on as temperatures drop to a few degrees above freezing, then off when they rise 3-5 C above that. You’ll hardly use any electricity keeping things frostfree.
You can make the system even more economical by adding foam pipe insulation on the outside of the ABS. One more tip: Use PEX pipe for your water line. PEX is one of the few pipes that won’t crack if something goes wrong and the water it carries freezes.
Visit baileylineroad.com/25834 for a video tour of one of the freeze-proof systems I have installed. Steve Maxwell is the editor of Pro Painter magazine and loves the smell of latex paint. Sign up for his free Saturday morning hands-on how-to newsletter at BaileyLineRoad.com