Hydro vs furnace? And rigid strips on the inside?
Hello, I have two unrelated questions.
First, in a home with walls approaching R-40 and roof at R-60, that is relatively “tight”, should we consider a modulating boiler/hydro air heating system? Or is a modulating furnace a better option keeping costs in mind? I guess what I am asking is, is there any truth to a furnace providing a “dry” heat, compared to a hydro system? And, if so should it be a consideration in the decision making process?
Second, having had numerous board contractors complain about installing blue board over walls with dense packed cellulose excessively stuffed behind netting, we proposed ripping thin strips (approx 2″) of 1″ rigid insulation to be installed over the interior of the studs, over the netting, so that the bulging between the bays now won’t interfere with the blue board installation. The board can then be fastened by screwing through the rigid into the stud with longer screw. Are there any draw backs to this process? Is there any significant thermal bridging break that could be considered due to this process assuming the exterior of the house is not wrapped with rigid?
Thank you.
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Replies
James,
To try to answer your first question, we need to clarify our terminology to distinguish between three ways to heat a house:
1. It's possible to heat a house with a boiler hooked up to a hydronic distribution system (either hydronic baseboard units or in-floor radiant tubing). Let's call this a hydronic system.
2. It's possible to heat a house with a furnace hooked up to ductwork. Let's call this a forced-air system or a system with a furnace.
3. It's possible to heat a house with a boiler hooked up to a ductwork distribution system; such systems include a heat-exchange coil in the air handler. Hot water circulates through the heat-exchange coil, and the air handler blows warm air past the coil and through the ductwork. Let's call this a hydro-air system.
Now, to address your questions.
Q. "Is there any truth to a furnace providing a 'dry' heat, compared to a hydro system?"
A. No.
Q. "Should it be a consideration in the decision-making process?"
A. No. Any one of the three systems I described can heat your house comfortably. There's nothing wrong with choosing the cheapest of the three options. Creating a tight, well insulated thermal envelope is far more important than the differences between these three types of heating systems.
Q. "The board can then be fastened by screwing through the rigid into the stud with longer screws. Are there any drawbacks to this process?"
A. No thermal or physical drawbacks, once the work is done. But there's a lot of added labor -- that's a drawback.
Q. "Is there any significant thermal bridging break that could be considered due to this process assuming the exterior of the house is not wrapped with rigid?"
A. I don't understand this last question. Perhaps you can rephrase it.
Martin,
Thank you. Sorry for the lacking terminology on my end. Regarding the heating systems, I was trying to compare the systems you describe in numbers 2 and 3 of your reply, thank you for the feedback, it is very helpful.
On my last question, in my limited understanding, I thought one of the benefits of rigid insulation on the exterior, in addition to the added R value, was the "thermal break" (not sure on this terminology) it provided from the exterior to the wall and the inside of the house, not allowing the cold to transfer through the studs to the inside. So I thought, instead of just furring the inside studs out with strapping to account for the cellulose bulge, would there be an added value to using polyiso, or similar, to fur out as that would potentially provide that "thermal break" between the outside of the wall and inside of the stud. I am sorry if this isn't making sense.
Best,
Jim
Jim,
Now I understand your question. Yes, strips of foam on the interior sides of the studs will provide an effective thermal break. Just be sure that your sheetrockers are on board with your plan -- some drywall contractors hate screwing through foam.
Will do, thank you again.
J
I've read of special rollers, made just for the bulging problem. Apparently they flatten the bulge out pretty well. Any opinions here on their merits?