Make-up combustion air rqmt.

[Bob Fuhrmann]

Lots of older homes do not have combustion make-up air vents installed. Is there a reqmt. to install them upon transfer of title (selling the home)? Is there a reqmt. to install them upon installation of a new (just like the old one) furnace installation?

[Nick Ostrowski]

True, many older homes don't have combustion makeup ventilation installed where needed but they should even if it was not a requirement when the house was built. I don't know of any area that requires provisions for combustion makeup air as part of a title transfer. But newer construction and many newer HVAC installations should have them installed as needed. Whether or not it is required for title transfer really shouldn't matter. If a system needs combustion makeup air vents installed to operate properly, it should be done.

[Bob Fuhrmann]

The home has been operating with out make up vents for 40 years. I agree that they should be installed, but my ? is: "Is there a documented requirement to install them if not installed now". Does the mechanical code address this?

[Jim Robinson]

That's going to be on a state by state basis, and it's a "no, not required" in my state. Probably not in very many states, either.

[Jim Luttrall]

Yes, when you replace the furnace, you must provide combustion air. No way it will pass local code inspection without it unless the local AHJ is blind. Even if the local AHJ misses it, the licensed installer is REQUIRED to make sure it is a safe installation that meets minimum code.

There has always been a requirement for combustion air (at least for more than 40 years) and depending on your local code at the time there were many options. There still are many options. If it has been working properly for 40 years and no one has died yet, then chances are one of the alternatives is in place but may not be recognized by an inexperienced inspector or by the current code.

[Jerry Peck]

Even if the local AHJ misses it, the licensed installer is REQUIRED to make sure it is a safe installation that meets minimum code.

And those requirements will be in the installation instructions, and the installation instructions are code by reference.

And the new furnace is *required* to be installed in accordance with its installation instructions *and* the code, the most restrictive shall apply.

So, yes, make up air would be required to meet the code at the time of installation of the new furnace.

[Jim Robinson]

To clarify, I was answering regarding the transfer of title part of the question. Installing a new furnace would require that the current CA requirements be met.

[Tim Spargo]

This was from yesterday.... new home, just receiving COO.

Oh, by the way, the system is an R-22. How are they getting away with? I was saddened the AHJ suggested this "fix"... there were no CA vents in the closet, but the attic was well vented, accessible and there was no reason to suggest a fix that is substandard in nature IMO, let alone by the AHJ.

I was there... explaining @ same time... kinda, well AWKWARD:confused:

[Steve Zabarylo]

This was from yesterday.... new home, just receiving COO.

Oh, by the way, the system is an R-22. How are they getting away with? I was saddened the AHJ suggested this "fix"... there were no CA vents in the closet, but the attic was well vented, accessible and there was no reason to suggest a fix that is substandard in nature IMO, let alone by the AHJ.

I was there... explaining @ same time... kinda, well AWKWARD:confused:

Even if this were an induced draught system it would just be wrong. When the draw from the return back draughts the burners and the occupants are terminated by CO poisoning will the AHJ still think it's a good idea? If it's a direct vented unit then the space at the bottom of the door could at least be justified to reduce heat buildup in the closet.

[Tim Spargo]

Yep... just a reg induced..

Maybe originally they were gonna use a condensing type or one that draws air in via a intake pipe etc..

I was standing there... in awe, I let the client know what should be done and if a 2" gap ends up at bottom of door, I included some advice as well.

[John Walker]

CHAPTER 7
COMBUSTION AIR
SECTION 701
GENERAL
The provisions of Chapter 7 shall apply to fuel burning
equipment installed in buildings and that require air for combustion,
ventilation, and dilution of flue gases from within
the building.
Exception No. 1: Direct vent equipment that is constructed
and installed so that all air for combustion is
obtained from the outside atmosphere and all flue gases
are discharged to the outside atmosphere.
Exception No. 2: Enclosed furnaces that incorporate an
integral total enclosure and use only outside air for combustion
and dilution of flue gases.
Equipment shall be located so as not to interfere with proper
circulation of combustion, ventilation, and dilution air.
Where normal infiltration does not provide the necessary air,
outside air shall be introduced.
In addition to air needed for combustion, process air shall be
provided as required for cooling of equipment or material,
controlling dew point, heating, drying, oxidation, dilution,
safety exhaust, odor control, and air for compressors.
In addition to air needed for combustion, air shall be supplied
for ventilation, including all air required for comfort and
proper working conditions for personnel.
A draft hood or a barometric draft regulator shall be installed
in the same room or enclosure as the equipment in such a
manner as to prevent any difference in pressure between the
hood or regulator and the combustion air supply.
Air for combustion, ventilation, and dilution of flue gases for
gas utilization equipment vented by natural draft shall be
obtained by application of one of the methods covered in
Sections 703 and 704.
Air requirements for the operation of exhaust fans, kitchen
ventilation systems, clothes dryers, and fireplaces shall be
considered in determining the adequacy of a space to provide
combustion air requirements.
SECTION 702
EQUIPMENT LOCATED IN UNCONFINED SPACES
Equipment located in buildings of unusually tight construction
(See definitions in Section 202) shall be provided with
air for combustion, ventilation, and dilution of flue gases
using the methods described in 703.2, 704, or 705.
SECTION 703
EQUIPMENT LOCATED IN CONFINED SPACES,
UNCONFINED SPACES
703.1 All Air From Inside the Building. The confined
space shall be provided with two permanent openings
communicating directly with an additional room(s) of sufficient
volume so that the combined volume of all spaces
meets the criteria for an unconfined space. The total input
of all gas utilization equipment installed in the combined
space shall be considered in making this determination.
Each opening shall have a minimum free area of 1 square
inch per 1,000 Btu per hour (22 cm2 per kW) of the total
input rating of all gas utilization equipment in the confined
space, but not less than 100 square inches (645 cm2).
One opening shall commence within 12 inches (30 cm) of
the top, and one opening shall commence within 12 inches
(30 cm) of the bottom, of the enclosure (see Figure
703.1). The minimum dimension of air openings shall be
not less than 3 inches (8 cm).
FIGURE 703.1
EQUIPMENT LOCATED IN CONFINED SPACES; ALL AIR FROM
INSIDE THE BUILDING
703.2 All Air From Outdoors. The confined space shall
communicate with the outdoors in accordance with methods
1 or 2. The minimum dimension of air openings shall
not be less than 3 in. (8 cm). Where ducts are used, they
shall be of the same cross-sectional area as the free area of
the openings to which they connect.
1. Two permanent openings, one commencing within
12 inches (30 cm) of the top, and one commencing
within 12 inches (30 cm) of the bottom, of the
enclosure shall be provided. The openings shall
communicate directly, or by ducts, with the outdoors
or spaces (crawl or attic) that freely communicate
with the outdoors.
FLORIDA BUILDING CODE — MECHANICAL 7.1
FIGURE 703.2(a) – FIGURE 703.2(c)
a. Where directly communicating with the outdoors,
or where communicating to the outdoors
through vertical ducts, each opening
shall have a minimum free area of 1 square
inch per 4,000 Btu per hour (5.5 cm2 per kW)
of total input rating of all equipment in the
enclosure. (See Figures 703.2(a) and
703.2(b).)
b. Where communicating with the outdoors
through horizontal ducts, each opening shall
have a minimum free area of 1 square inch per
2,000 Btu per hour (11 cm2 per kW) of total
input rating of all equipment in the enclosure.
(See Figure 703.2(c).)
2. One permanent opening, commencing within 12 in.
(30 cm) of the top of the enclosure, shall be permitted
where the equipment has clearances of at least 1
in. (2.5 cm) from the sides and back and 6 in. (16
cm) from the front of the appliance. The opening
shall directly communicate with the outdoors or
shall communicate through a vertical or horizontal
duct to the outdoors or spaces (crawl or attic) that
freely communicate with the outdoors, and shall
have a minimum free area of:
a. 1 sq in per 3000 Btu per hr (7 cm2 per kW) of
the total input rating of all equipment located
in the enclosure, and
b. Not less than the sum of the areas of all vent
connectors in the confined space. (See Figure
703.2(d)).
FIGURE 703.2(a)
EQUIPMENT LOCATED IN CONFINED SPACES; ALL AIR FROM
OUTDOORS — INLET AIR FROM VENTILATED CRAWL SPACE
AND OUTLET AIR TO VENTILATED ATTIC
FIGURE 703.2(c)
EQUIPMENT LOCATED IN CONFINED SPACES; ALL AIR FROM
OUTDOORS
7.2 FLORIDA BUILDING CODE — MECHANICAL
FIGURE 703.2(b)
EQUIPMENT LOCATED IN CONFINED SPACES; ALL AIR FROM
OUTDOORS THROUGH VENTILATED ATTIC
FIGURE 703.2(d)
EQUIPMENT LOCATED IN CONFINED SPACES; ALL AIR FROM
OUTDOORS. (ONE OPENING)
SECTION 704
COMBINATION OF AIR FROM INSIDE AND FROM
OUTDOORS
Where the building in which the fuel-burning appliances are
located is not unusually tight construction and the communicating
interior spaces containing the fuel-burning appliances
comply with all of the requirements of Section 703.1, except
the volumetric requirement of Section 703.1, required combustion
and dilution air shall be obtained by opening the
room to the outdoors utilizing a combination of inside and
outdoor air prorated in accordance with Section 704.6.
Openings connecting the interior spaces shall comply with
Sections 703.1. The ratio of interior spaces shall comply with
Section 704.5. The number, location and ratios of openings
connecting the space with the outdoor air shall comply with
Sections 704.1 through 704.4.
704.1 Number and location of openings. At least two openings
shall be provided, one within 1 foot (305 mm) of the ceiling
of the room and one within 1 foot (305 mm) of the floor.
704.2 Ratio of direct openings. Where direct openings to the
outdoors are provided in accordance with Section 703.2,
method la, the ratio of direct openings shall be the sum of the
net free areas of both direct openings to the outdoors, divided
by the sum of the required areas for both such openings as
determined in accordance with Section 703.2, method la.
704.3 Ratio of horizontal openings. Where openings
connected to the outdoors through horizontal ducts are
provided in accordance with Section 703.2, method lb,
the ratio of horizontal openings shall be the sum of the net
free areas of both such openings, divided by the sum of
the required areas for both such openings as determined in
accordance with Section 703.2, method lb.
FIGURE 703.2(d)-707
704.4 Ratio of vertical openings. Where openings connected
to the outdoors through vertical ducts are provided
in accordance with Section 703.2, method la, the ratio of
vertical openings shall be the sum of the net free areas of
both such openings, divided by the sum of the required
areas for both such openings as determined in accordance
with Section 703.2, method la.
704.5 Ratio of interior spaces. The ratio of interior
spaces shall be the available volume of all communicating
spaces, divided by the required volume as determined in
accordance with Section 703.1.
704.6 Prorating of inside and outdoor air. In spaces that
utilize a combination of inside and outdoor air, the sum of
the ratios of all direct openings, horizontal openings, vertical
openings and interior spaces shall equal or exceed 1.
SECTION 705
SPECIALLY ENGINEERED INSTALLATIONS
The requirements of 703 shall be permitted to be waived
where special engineering, approved by the authority having
jurisdiction, provides an adequate supply of air for combustion,
ventilation, and dilution of flue gases.
SECTION 706
LOUVERS AND GRILLES
In calculating free area in 703, consideration shall be given to
the blocking effect of louvers, grilles, or screens protecting
openings. If the free area through a design of louver or grille
is known, it shall be used in calculating the size opening
required to provide the free area specified. If the design and
free area are not known, it shall be assumed that wood louvers
will have 20-25 percent free area and metal louvers and
grilles will have 60-75 percent free area. Louvers and grilles
shall be fixed in the open position or interlocked with the
equipment so that they are opened automatically during
equipment operation.
SECTION 707
COMBUSTION AIR DUCTS
Combustion air ducts shall comply with (1) through (5).
1. Be of galvanized steel complying with Chapter 6 or of
equivalent corrosion-resistant material approved for
this application.
Exception: Within dwellings units, unobstructed
stud and joist spaces shall not be prohibited from
conveying combustion air, provided that not more
than one required fireblock is removed.
2. Terminate in an unobstructed space allowing free
movement of combustion air to the appliances.
FLORIDA BUILDING CODE — MECHANICAL 7.3
708 – 708.2
3. Serve a single enclosure.
4. Not serve both upper and lower combustion air openings
where both such openings are used. The separation
between ducts serving upper and lower combustion air
openings shall be maintained to the source of combustion
air.
5. Not be screened where terminating in an attic space.
SECTION 708
INSTALLATION
708.1 Installation/Instructions. Appliances shall be
installed in accordance with the manufacturer's installation
instructions which shall be available on the job site at the
time of inspection.
708.2 Public Garages/Parking Structures. Appliances
shall be installed in accordance with the manufacturer's
instructions and NFPA 88B.
7.4 FLORIDA BUILDING CODE — MECHANICAL

[Jerry Peck]

CHAPTER 7
COMBUSTION AIR
SECTION 701
GENERAL

John,

That is from the Mechanical Code, this thread is regarding a dwelling unit which is covered by the Florida Building Code, Residential (which does have similar or the same language, it's just the the proper code should be applied).

I don't have the codes on this computer, but the codes are available for free online if reference to the codes is required.

[James Duffin]

In NC the fuel gas code allows the one opening method.....


304.6.2 One-permanent-opening method. One permanent
opening, commencing within 12 inches (305 mm) of
the top of the enclosure, shall be provided. The appliance
shall have clearances of at least 1 inch (25 mm) from the
sides and back and 6 inches (152 mm) from the front of the
appliance. The opening shall directly communicate with the
outdoors or through a vertical or horizontal duct to the outdoors,
or spaces that freely communicate with the outdoors
(see Figure 304.6.2) and shall have a minimum free area of 1
square inch per 3,000 Btu/h (734 mm2/kW) ofthe total input
rating of all appliances located in the enclosure and not less
than the sum ofthe areas of all vent connectors in the space.

[Bob Harper]

I know we have to install MUA per code but just understand, it has been proven to be wholly unreliable and sometimes dangerous. The only system proven by ASHRAE that works is mechanical MUA interlocked to the appliance.