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Damaged rim joist - what is the best way to repair?

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tagal4

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I recently had a new "high efficiency" furnace installed and the subcontractor that did it bored two VERY LARGE holes for the PVC vent and supply pipes adjacent to the top edge of my house's rim joist, one of which is right under the king and jack studs for a window. It bothered me a lot after I saw what had been done so I looked it up, and from what I've read this is something a person definitely shouldn't do. I'm wondering the best way to fix this. My thought is to remove the pipes and make some plugs out of 2X stock and glue them in the holes to eliminate the gaps in the top of the joist to try to regain the structural strength lost. Also to possibly screw some plywood or a piece of 2 X 10 to the inside of the damaged area. Or am I going to need to replace part of all of the joist? Obviously the holes need to be relocated to a better location and bored through the CENTER of the joist.

Any thoughts on the logic of installing high efficiency furnaces that have been way over-sized for the house they go in? This subcontractor installed a furnace 50% larger than what was ordered by the contractor because he said his supplier was out of the smaller size. Seems to me having a correctly sized 80% efficient furnace would be better than having a high efficiency furnace that was grossly over-sized.

Obviously this subcontactor didn't know what he was doing and this has been a very frustrating experience.

Thanks for any help.
 

bud16415

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Welcome to the forum.

I wouldn't be worried about the holes. The bottom plate IMO will spread the load enough.

As to the furnace I also don't think it will be a problem, but others here more up on furnace selection can chime in.
 

Steve123

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If your furnace has 50% more BTU capacity, it will also flow 50% more air, and have corresponding more airflow noise. If its a higher end model it probably has a variable speed blower, and maybe a variable gas valve. The contractor should then be able to dial it down. However, if your AC condenser is also over-sized, the you would be limited in how much you can dial down the summer airflow. The AC coil needs a certain amount of airflow to avoid it freezing up.
 

tagal4

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Yes, this furnace blows air like there is no tomorrow. I can feel it across the room, and it actually makes it feel less comfortable in the rooms of my than with my old furnace because of all the air extra circulation.
 

bud16415

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What was your old furnace? I also noticed increased air flow with the increase in efficiency it also seemed the heat in the airflow was less. I remember the days of gravity feed and the air coming out would cook your feet if you stood on the grate. The nature of increased efficiency is in lowering the exhaust gasses to extract more heat to the point even it is safe to go thru PVC pipe rather than up a brick chimney lined for high temps. When you lower the exhaust heat (waste) it is done by sending greater amounts of cooler air into the building. That and most older homes all the duct work was sized for the older furnace.

My point is some of what you are seeing could be the over sized unit and some can be the new technology.
 

tagal4

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I originally had a large gravity furnace with 8" ducts running out from the top of it. Then I switched to an "80+" forced air furnace with a plenum I had custom made for it and reduced the duct size to 6" and used reducers to adapt them to the existing registers (which I think are classy looking).
 

bud16415

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I could be wrong and i'm not a furnace guy just an avid DIYer.

When a furnace extracts more heat out of the combustion the air it sends out is equal or slightly lower than the waste gasses. They are extracting heat lower than the dew point even (I believe) and that's the reason for the little pumps to pump out waste water. With lower heating air temp they need to make up the total BTU put in the house by greater air flow.
 

bud16415

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If your furnace has 50% more BTU capacity, it will also flow 50% more air, and have corresponding more airflow noise. If its a higher end model it probably has a variable speed blower, and maybe a variable gas valve. The contractor should then be able to dial it down. However, if your AC condenser is also over-sized, the you would be limited in how much you can dial down the summer airflow. The AC coil needs a certain amount of airflow to avoid it freezing up.
If a furnace does have speed controls where the air flow to the room would be reduced is it possible to have it run different speeds when set to heat and cool?

Am I correct in thinking (see above) that the higher the efficiency more air has to be moved?
 

tagal4

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I'm starting to think this "high efficiency" gas furnace idea might not be all it's cracked up to be. I have read they (at least the single stage ones) are actually less efficient than an 80% two gas stage furnace since they usually run on the low stage most of the time whereas the high efficiency ones run full blast all the time when they come on.

I wish I would have gone with some kind of an electric heat pump instead. I hate having to heat my house with fracked gas and all the problems that causes. In the area where I live we get a sizable portion of our electricity from renewables, and that is likely to keep going up. I doubt it will be too much longer and gas furnaces will be like gas clothes dryers - almost non-existent.
 

Jeff Handy

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Bring in another hvac guy with a good local reputation.
He can probably adjust your furnace to blow less powerfully but for longer cycles, which is more comfortable for you.
More even heating and less breezy.
I think I would add another joist over the weak spot, sistered on with glue and screws.
Or two or three 3/4 inch plywood pieces cut to match, also glued and screwed.
Leave the pipes how they are, just cut them to allow the repair pieces to be installed, then repair the cut pipes.
 

Steve123

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If a furnace does have speed controls where the air flow to the room would be reduced is it possible to have it run different speeds when set to heat and cool?
Am I correct in thinking (see above) that the higher the efficiency more air has to be moved?
Probably varies by furnace model. Any furnace I would even remotely consider would have at least multi-speed blower motor. I have bought two furnaces in the last 8 years (two houses) and both had variable speed motors, variable gas valves, and computerized controls with a huge amount of settings for heat, cool, and blower. The AC settings would be totally separate from the heat settings. The settings are done by the installer, not the home-owner.

I don't think higher efficiency necessarily means moving more air. A lot of the higher efficiency is just using external air for combustion --- old furnaces use internal air for combustion, and for every cubic foot of combustion air exhausted, you will suck a cubic foot of cold, dry air into the house through ever present cracks and gaps.
 

ekrig

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I'm starting to think this "high efficiency" gas furnace idea might not be all it's cracked up to be. I have read they (at least the single stage ones) are actually less efficient than an 80% two gas stage furnace since they usually run on the low stage most of the time whereas the high efficiency ones run full blast all the time when they come on.
I don't know what kind of "high efficiency" furnace you got, but I don't anything more than a 2 or 3 stage furnace helps much, if at all. If does help the manufacturers and contractors because they get you locked into a specific technology. When I replaced mine, I went with their very high efficiently, which is mainly achieved by a fully variable blower, but now I'm stuck with their proprietary thermostat. Since it is a new furnace, it heats much better than the old 1-stage one (which was falling apart anyways) but the old Honeywell thermostat that we had actually managed to make it feel more comfortable.

I wish I would have gone with some kind of an electric heat pump instead. I hate having to heat my house with fracked gas and all the problems that causes. In the area where I live we get a sizable portion of our electricity from renewables, and that is likely to keep going up. I doubt it will be too much longer and gas furnaces will be like gas clothes dryers - almost non-existent.
I'm afraid you are being a victim of wishful thinking. Gas has been produced using fracking for almost 50 years and, apart from irresponsible companies gambling with regard to safety risks, the risks are perhaps comparable to those of wind turbines and the environmental problems that they create (or the pollution associated with producing solar panels). Of course, effective regulation and its enforcement is paramount. In any event, the current levels of renewables are possible because the grid is backed by an extensive network of power plants running on natural gas. Don't take my word for it. There are multiple studies by professors at Stanford and Princeton trying to understand what that transition would entail, and gas power plants are a crucial part of that balance. I agree with you that we will drastically reduce the amount of fossil fuels that we use but, considering that effective, scalable, and cost-effective technology leads do not even really exist for energy storage, that is going to be a long transition of 20-30 years. Even if the technology existed, grid-level changes take on the order of 10 years for scaling up.
 
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