Homeowner questions straight from the attic

Question:
When the temperatures get below zero, we have loud banging noises coming from the attic. The noise occurs all over the house. Sometimes it sounds like the rafters are cracking. Sometimes the noise is so loud it frightens me.

One time last night the noise was so loud I jumped out of bed, turned the light on, and thought about getting dressed in case I have to leave the house in a hurry. I didn’t sleep the rest of the night, waiting for the proverbial “other shoe to drop.” Is there something wrong with my house? Do other people have the same thing happen? What causes this noise to happen? Can anything be done about it? I would appreciate any information you can provide.

Answer:
That is a very common problem when there is a rapid change in temperature. Judging by the date of your email, the temperature was 50 degrees one day and, after a cold front came through, it was 5 degrees the next morning. This rapid drop caused a contraction in the roof decking and the rafters that was so fast the wood did not have time to move slowly, in small increments under the nails. Instead, it jumped, causing the loud cracking noise you heard. The best fix we can suggest for you is earplugs.

Question:
Our furnace kept on working but not heating last week. The repairman determined the air pipe was probably frozen and cut the pipe inside the furnace room. He said when we feel cold breeze coming from the pipe, to call him to come back “to re-hook the pipe up and insulate supply and intake in the attic.”

He also wants to replace the pressure switch that got wet. The quote for 60’ of 2” insulation and the pressure switch is over $500. Since the pipe was cut, the furnace is working fine. No breeze is coming out yet, nor unfrozen water. The club house was built in 2005. The furnace is Lenox 90+up, model g43UF-36b-070-06, serial 5905 E18667.

Answer:
With the information supplied, we can’t tell you exactly what the problem is. We know your furnace is a high efficiency model. These models have one plastic pipe to bring outside air to your furnace for combustion rather than use the air inside your house which has been heated. There is a second plastic pipe that brings the combustion gas back outside your house. These two pipes should be the same length to balance the pressures. It does appear there is a restriction that was sensed by the pressure switch that then shut off the gas. There are several possible causes of this. Snow could block the entrance to the pipe, or a bird or other animal could block this pipe.

There is also a manufacturer’s bulletin that describes crystal-like deposits at the inlet of the pressure switch ports that can activate the pressure switch. Their fix is to replace the cold-end header box with one that has a larger pressure switch port that greatly decreases the forming and bridging of these crystal-like deposits. The cold-end header box should be replaced only if the pressure switch ports are plugged. If the furnace is still under the factory warranty, the replacement cold end header box can be ordered under warranty.

Two things that you mention do not sound correct. If the furnace is now working, the pressure switch is probably not bad. We do not see any way insulation around the inlet air pipe can help. In very cold weather the snow is light and fluffy and can accumulate on the inlet screen and block the pipe, but this is outside and would not be helped by attic insulation.

Cutting the air inlet pipe should only be a temporary diagnostic measure that should be repaired as soon as the plug can be removed. With the information supplied we would recommend getting a second opinion from a qualified service technician.

Tip: If you didn’t replace the batteries in your smoke alarms on Jan. 1, replace them this month. If your smoke alarms are over 10 years old replace them this month as they are beyond their lifespan and may no longer be working.

• If you have suggestions for future tips or have questions about maintenance around your home submit them to ask.the.woodchucks@gmail.com

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