Saturday, June 24, 2017

Why Is There Mold Around The Air Conditioning Vents?

The louvered metal grille that directs conditioned air from a duct into the room is called a register, and mold around an air conditioning register can have several causes:

1) If the cold air coming out of the register is too cold compared to the room air, condensate will form on the surface of the register and migrate over to the surrounding drywall. Wet drywall will begin to grow mold within a few days.

The difference between the room air and cold air coming out of the register is called the “temperature differential” or “split,” and more than about a 22ยบ F split will cause condensate to form.

2) Duct air leakage above the register or at the connection of the duct to the register can also cause condensate to form, even if the temperature split is not excessive, because the air in the unconditioned attic or wall cavity may be significantly warmer. If squirrels or rodents get into the attic, they may shred openings in ducts for material to make their nests. Workmen in the attic also occasionally cause duct damage that leads to leakage.

3) Closing the louvers of the register completely—to shut off air conditioning to a room—can also lead to mold growth.

Mold around an air conditioning register is a good reason to call a licensed air conditioning contractor for evaluation and repair before the problem causes damage that requires more expensive mitigation.

Wednesday, June 21, 2017

Why Can't I Use My Home's Central Air Conditioning System To Cool The Garage?

Tapping into your air conditioning system to add a couple of ducts may seem like an excellent idea if you if have a garage workshop, but it is not allowed by the building codes. The International Residential Code (IRC) and Florida Building Code (FBC - R302.5.2) both state that residential air conditioning ducts “shall have no openings in the garage.” The reason is fire safety. Garage fires tend to spread farther and cause more injuries and dollar loss per fire than fires that start in all other areas of the home, according to the U.S. Fire Administration.

So the building codes have multiple requirements intended to maintain a fire separation between a dwelling and an attached garage, particularly focused on making sure that there are no openings or penetrations through the walls and ceiling between the house and garage that would allow a fire to spread into the house. An air conditioning duct is a route that provides a direct air connection to the house if a/c vents/registers are installed, allowing a quick spread of fire and fumes into the home.

There are other good reasons not to run a/c ducts out to serve a garage, including that your system was not designed for serving about 20% more square footage, garage doors leak air and are difficult to seal, and—because return air ducts would pull garage fumes into the house—the lack of return air would simply pressurize the garage and do a poor job of reducing the temperature.

Cooling down your garage with a mini-split (ductless) air conditioner or wall unit is fine, just don’t use your home’s central a/c system.

Monday, June 19, 2017

Does An Attic Access Opening/Hatch In A Garage Have To Be Fire Rated?

The garage is recognized by fire officials and the building code as a place where plenty of house fires get started. Flammable liquids, such as gasoline, paint thinner, degreaser, and other solvents, are often stored in a garage. A car in the garage can leak gasoline onto the floor, and the gas itself or its vapor is easily ignitable by a spark. So the Florida Building Code (FBC) and International Residential Code (IRC) have safety standards for maintaining a separation for fire protection between a garage and the house, to keep any garage fire from quickly spreading into the home.

One of the separation requirements is that the ceiling of a garage should be “not less than 1/2-inch gypsum board or equivalent.” Any openings for attic access in the garage ceiling must also meet this standard, so an attic hatch cover panel of 1/2-inch gypsum board obviously meets this requirement, but there is also fire-treated plywood that can be used. Fire-rated attic ladders with a 30-minute burn rating are another alternative. What is not acceptable is a panel of regular plywood or other readily flammable material for an attic hatch cover in a garage.

Saturday, June 17, 2017

Why Is A Garage Floor Sloped?

It makes practical sense for drainage, especially if you hose down your garage floor every once in a while, but also happens to be required by the both the Florida Building Code (FBC) and International Residential Code (IRC). The slope is only necessary for the area where a vehicle is parked. It can be sloped either to the garage door or a floor drain, and the amount of slope is not specified. Here’s how the building code states it:

Wednesday, June 14, 2017

Does An Electric Recepticle Outlet In A Storage Shed Require GFCI Protection?

The National Electrical Code [NEC 210.8 (A)(2)] requires a ground fault circuit interrupter (GFCI) protection for “all 125-volt, single-phase, 15- and 20-ampere receptacles” installed in “accessory buildings that have a floor located at or below grade level not intended as habitable rooms and limited to storage areas, work areas, and areas of similar use.” That pretty clearly defines a detached storage shed and means any receptacles inside should be GFCI-protected. It has been argued, but unsuccessfully, that a shed mounted on skids does not constitute “on grade.”

Since a backyard shed may have the closest available receptacle for plugging in electric gardening tools like a string trimmer, lawn mower, or leaf blower, making sure that it has the wet-environment shock protection provided by a GFCI just makes good sense.

Saturday, June 10, 2017

What Is A 'Continuous Load Path'?

Most people think of the structural failure of a house as collapse. But falling down is only one way a structure can fail, and gravity is not always the culprit. A building can also fail upwards, when a hurricane creates a pressure imbalance that literally sucks off the roof; and it can fail sideways, when high winds cause lateral pressure that makes a gable end wall hinge away from the rest of a wall assembly and fall over. A earthquake can also put severe lateral and uplift loads on a house.

Nails are the traditional connectors for the wood structural components of a house, and they are excellent at keeping wood framing snug and aligned so that the weight of the structure, its furnishings, and occupants can be reliably transferred down to the ground without anything shifting. But nails do not work as well for uplift and lateral loads because they are often in what engineers call “withdrawal,” which means that when these unusual loads are applied they are typically in the opposite direction of the way that the nail was hammered into the wood and the nails simply “pull out” with little resistance.

To avoid failure of a house structure from uplift and lateral loads each piece, from the roof down to the foundation, must be securely connected together like the links of a chain. This is called a continuous load path and, also like a chain, it is only as strong as its weakest link.

Both metal connector plates and structural wood panel sheathing are used in a wood stud-framed house to create a continuous load path. The illustration below shows examples of the typical metal connectors to create a secure load path from the base plate up to the roof trusses.

A concrete block house utilizes concrete columns and concrete-filled cells with steel reinforcement running from the foundation/floor slab to the tie beam, then metal connectors to the wood components above it, to tie everything together. Constructing a continuous load path is a building code requirement.

Thursday, June 8, 2017

What Is The Difference Between A Carport And A Garage?

Most people would define a garage as a completely enclosed room with a garage door for parking a car out of the weather, while a carport is a roofed-over parking space with open sides.

When a carport is attached to a house, it usually has two or three open sides. But the International Residential Code (IRC) and Florida Building Code (FBC) have a very specific way of defining the difference between carport and garage:

This means that as soon as you add a third wall to a carport, like in the photo below, it becomes a garage and must meet all the fire safety standards required of a garage.

The fact that the fourth side is open and there is no garage door does not make a difference. Because flammable materials are often stored in an attached garage, there are multiple code requirements intended to enhance the resistance of the walls and ceiling to the spread of a garage fire into the living area of a home.