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Furnace Replacement

S

StephNow

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Joined
Oct 20, 2009
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75
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Home of Larry Holmes
When a furnace is being replaced in an older home, not adding refrigeration, all of the duct is in place, not damaged and does not have other issues, but there is no insulation on the ducts in the unconditioned basement, do you require that the ducts meet the energy code requirements for minimum insulation?
 
What code are you under?

Your cryptic Longitude and latitude do not come up with results in this world.
 
& = & = &

snowroski,

If you are using the IRC, there is no requirement to insulate the existing ducting.

From the `12 IRC, Section N1101.3 (R101.4.3) - Additions, alterations,

renovations or repairs:

"Additions, alterations, renovations or repairs to an existing building, building

system or portion thereof shall conform to the provisions of this code as they

relate to new construction without requiring the unaltered portion(s) of the

existing building or building system to comply with this code.........Additions,

alterations, renovations or repairs shall not create an unsafe or hazardous

condition or overload existing building systems............An addition shall be

deemed to comply with this code if the addition alone complies, or if the

existing building and addition comply with this code as a single building."



Section R101.4.3 is not in the `12 IRC, ...don't know if the referenced

code section is a misprint or not.

A permit to replace the appliance, and inspection(s) of the project IS

required though !

While there is no "requirement" to install insulation on the existing

ductwork, ...in the interest of full transparency to the homeowner,

...the offer to install such insulation "could be" offered on the contract.

Provide the homeowner with accurate code information, and let them

decide what they want to do.



& = & = &
 
why do you think it is "unconditioned space"?

No the existing ducts do not need to be sealed or insulated

R403.2.1 Insulation (Prescriptive).

Supply ducts in attics shall be insulated to a minimum of R-8. All other ducts shall be insulated to a minimum of R-6.

Exception: Ducts or portions thereof located completely inside the building thermal envelope.

BUILDING THERMAL ENVELOPE. The basement walls, exterior walls, floor, roof and any other building element that enclose conditioned spaces.

Put a few registers in and condition the space
 
In Pennsylvania, local ordinance requires permit for the replacement of furnace. Sorry for the coordinates (just checked and they don't lead to the correct location anyway). I am coming across property owners who have or are going to be replacing furnaces and the previous inspection agency has been failing the installation because the ducts were not insulated.

I have not required the insulating of ducts with a furnace swap, but got worried that I was missing something.

Thanks!
 
I agree with steveray, if registers are added to make conditioned space, now you have to size the equipment for the additional heating load and create the thermal envelope for the conditioned space.
 
The uninsulated and leaky ducts have already created an existing partially conditioned space. Many basements have been partially heated by heat off the furnace boiler and ducts. It is a feature not a bug.
 
The only thing we have made people upgrade as part of a furnace upgrade was the flue. It was an old leak masonry chimney and I was worried the new, more efficiency equipment would not have flue gases hot enough to create the draw necessary and potentially combustion gas spillage into the home. Turns out they had already planned on putting an insert in the old chimney, so it was a non-issue. If it doesn't deal directly with life safety, I recommend changes, but stop short of requiring them.
 
Conundrum... Size the new furnace for the heated living space and the unit will likely be under-sized and over-worked.

Size based on the existing conditions and then have a system that still won't work properly, won't save the owner anything on their heating bill only to come back later and tighten up the ducts to leave them with a now oversized unit that still won't be efficient...

OR.... have an Energy Audit done by an independent company and see what the best course of action really is.

(P.S. I think NYS has an amendment that would address this)
 
mtlogcabin said:
why do you think it is "unconditioned space"?No the existing ducts do not need to be sealed or insulated

R403.2.1 Insulation (Prescriptive).

Supply ducts in attics shall be insulated to a minimum of R-8. All other ducts shall be insulated to a minimum of R-6.

Exception: Ducts or portions thereof located completely inside the building thermal envelope.

BUILDING THERMAL ENVELOPE. The basement walls, exterior walls, floor, roof and any other building element that enclose conditioned spaces.

Put a few registers in and condition the space
Click to expand...
No go. Conditioned spaces must be properly insulated so registers in basements then require the basement to be insulated. You can't have it both ways to circumvent a code requirement
 
JBI said:
Conundrum... Size the new furnace for the heated living space and the unit will likely be under-sized and over-worked. Size based on the existing conditions and then have a system that still won't work properly, won't save the owner anything on their heating bill only to come back later and tighten up the ducts to leave them with a now oversized unit that still won't be efficient...

OR.... have an Energy Audit done by an independent company and see what the best course of action really is.

(P.S. I think NYS has an amendment that would address this)
Click to expand...
Yes, the new unit must be properly sized for the conditions of the home that it will serve INCLUDING duct insulation, size, and thermal envelope.
 
jar546 said:
No go. Conditioned spaces must be properly insulated so registers in basements then require the basement to be insulated. You can't have it both ways to circumvent a code requirement
Click to expand...
2012 IRC

N1101.4 (R101.4.5) Change in space conditioning.

Any nonconditioned space that is altered to become conditioned space shall be required to be brought into full compliance with this chapter.

CONDITIONED SPACE. For energy purposes, space within a building that is provided with heating and/or cooling equipment or systems capable of maintaining, through design or heat loss/gain, 50°F (10°C) during the heating season and 85°F (29°C) during the cooling season, or communicates directly with a conditioned space. For mechanical purposes, an area, room or space being heated or cooled by any equipment or appliance.

If the basement already maintains a 50 degree f temp then nothing is required to be done to the basement walls or the duct system.

This is quite common in basements in my area of the country

MECHANICAL SYSTEM. A system specifically addressed and regulated in this code and composed of components, devices, appliances and equipment.

M1202.1 Additions, alterations or repairs.

Additions, alterations, renovations or repairs to a mechanical system shall conform to the requirements for a new mechanical system without requiring the existing mechanical system to comply with all of the requirements of this code. Additions, alterations or repairs shall not cause an existing mechanical system to become unsafe, hazardous or overloaded. Minor additions, alterations or repairs to existing mechanical systems shall meet the provisions for new construction, unless such work is done in the same manner and arrangement as was in the existing system, is not hazardous, and is approved.

The basement may already be conditioned by definition.

There are any number of things a homeowner does to their home that can positively or negatively effect the HVAC system. Have they installed new energy windows? Have they installed exterior insulation when residing the house? Did they add more blow in insulation in the attic? These are all questions the contractor needs to ask before determining the size of the HVAC unit. The additional heating load on the basement is minimal compared to the other issues. Is the original unit an old 80% and the new a 90% or 95% same size..

Remember this is not a new home and to do a designed system to the nats :butt size will not be possible. The contractor will have to err on the larger size of the calculated load range.
 
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