A: Composite decking materials are naturally lumped together but actually constitute different products and manufacturing techniques.
Polypropylene is made from hard plastics, both new and recycled, mixed with wood fiber.
Polyethylene is a softer plastic, the type we associate with recycled milk jugs. It also is mixed with wood fiber or can be found 100-percent pure.
Some of the problems that have been reported have to do with the untreated wood fiber. It can and does rot, despite being "encapsulated."
At least one manufacturer treats the wood fiber with borates, which certainly would seem to help.
But like any new building product, how well do we know in the long run? How many 10-year-old composite decks have we seen that still look good and perform as advertised?
Composite decking is not structural, so it tends to sag more than wood. This may require closer joist spacing. Like vinyl, it can get brittle and fade with UV exposure. It expands and contracts more than wood, and differently than the wood frame to which it is attached.
Most composite products cannot be sanded and refinished, which may be a positive or a negative depending on the size of the wine stain and the depth of the dog's claws.
The puzzler for me in the marketing hype is the claim that it lasts longer than treated wood. That would be interesting, since the frame it is attached to is built of treated wood. And then add on additional cost and construction complexity.
On the plus side, it doesn't necessarily need to be re-stained or even cleaned as often, isn't slippery generally, uses recycled and waste materials, does not give up slivers and looks great.
So what would I use? Cedar. I think composite has a great future, but we need more time on the clock.
Q: I recently moved into a house where the attic is uninsulated because it has knob and tube wiring. My plan is to rewire, but not this year.
My understanding is that it's not a good idea to put insulation around knob and tube wiring; however, I don't want to go through this winter without insulation.
My thought is to lay unfaced fiberglass insulation on top of the joists, then when I rewire, add faced insulation (with the faced side down) between the joists. In the end, I would have two layers of insulation.
Is it OK to use unfaced as the only layer of insulation in the attic? And what's your suggestion for R-value?
A: Just about every house built before WWII has some amount of knob and tube in the attic unless it has been gutted and completely rewired; those are few and far between.
In our area, you will find fewer than 1 in 100 attics without insulation. So somebody is insulating over knob and tube. And they aren't all burning up.
I am saying this with half a smirk, since insulating over knob and tube is perfectly acceptable and legal if it has been signed off by an electrician after inspection.
There are very few problems with knob and tube compared to what is seen with aluminum wiring, amateur electrical alterations and unsafe electrical panels.
But knob and tube gets all the attention. This is not to say that your proposed method is flawed in any way, but rather that there are options.
Unfaced in an older house should present you with no problems.
An appropriate R-value would depend on the wall insulation and windows — R-38 in the attic would be useless with leaky windows, drafty doors and uninsulated walls.
There are too many variables (and not enough information) to give you a complete answer. But R-19-30 is a good starting point that the typical older house would benefit by.
So get your wiring inspected and call your utility company, which may be able to offer you a low- or no-cost energy audit to help you find an appropriate insulation level and plan for improvement. |
