Ashrae 62.2 pdf free download

Examples include carbon dioxide and monoxide from gas-fueled appliances, radon gas from the soil surrounding foundations, formaldehyde from building materials and particulates such as mold and tobacco smoke. Table 1 lists some major sources of indoor and outdoor pollutants. Some of the more common pollutants deserve discussion on their creation and possible human health concerns. Carbon dioxide and carbon monoxide, resulting from combustion of fuel, can pose serious health problems. Older appliances usually generate the highest levels of carbon monoxide due to improper combustion, leaks and lack of enough fresh air for complete combustion.

While carbon dioxide only causes problems at high levels, its presence usually indicates carbon monoxide is also present. High carbon dioxide levels cause drowsiness and indicate poor ventilation. Carbon monoxide causes headaches and fatigue at low levels and may cause unconsciousness or death at high levels.

Ensuring an outside air supply for any combustion appliance and regular air exchanges alleviate the problems. Radon enters a structure through access holes for piping, floor cracks and other openings to the soil and results from the decay of naturally occurring radioactive materials in the soil. Radon has the potential to cause lung cancer at high levels.

Ventilating crawl spaces and basements with fresh air may reduce the problem, but the preferred method is to vent the gravel layer below the basement floor Figure 4.

A radon test should be conducted to determine the radon level. Figure 4. Radon venting. Other household airborne hazards are a result of construction materials and cleaners.

Formaldehyde, a common industrial chemical, is present in many building materials and household furnishings. The formaldehyde gas can leave materials and enter the environment throughout the lifetime of the material, but most of the gas leaves within the first year. Formaldehyde causes irritation in mucous membranes in the nose, throat and eyes. It needs to be vented to the outside. Formaldehyde use is restricted in construction materials today.

Particulates include larger airborne items such as the mold spores and tobacco smoke mentioned earlier. It also includes viral and bacterial organisms, pet dander, dust and many other things. Due to a large variety of items, physical ailments vary from colds to allergies to lung disease. Some particulates may be filtered out, but others can be vented only to the outside. One way to minimize air quality and moisture problems in a home, without opening a window, is by the installation of a mechanical ventilation system using an air-to-air heat exchanger.

An air-to-air heat exchanger brings two air streams of different temperatures into thermal contact, transferring heat from the exhausting inside air to incoming outside air during the heating season.

A representative heat exchanger is shown in Figure 5. In summer, the heat exchanger can cool and, in some cases, dehumidify the hot outside air passing through it and into the house for ventilation. The air-to-air heat exchanger removes the excess humidity and flushes out odors and pollutants generated indoors. Heat exchangers generally are classified by the way the air moves through the unit. In a counter-flow exchanger, hot and cold air streams flow parallel in opposite directions.

In a cross-flow unit, the air streams flow perpendicular to each other. An axial flow unit uses a large wheel. The air warms one side of the wheel, which transfers heat to the cold air stream as it slowly turns. A heat pipe unit uses refrigerant to transfer the heat. Other units are available for specialized applications.

Small structures, such as houses, generally use counter-flow or cross-flow exchangers. The majority of air-to-air exchangers installed in northern climates are heat recovery ventilators HRVs. These units recover heat from exhausted air and return it to the building. Recent advances in technology have increased the use of energy recovery ventilators ERVs as well. In the past, ERVs mainly were used in climates with higher humidity that have a heavier cooling than heating load.

ERVs have had problems with lower efficiencies due to oversaturation of internal desiccant wheels during longer periods of high humidity, but with proper installation and maintenance, they can create a healthier living space and greater energy savings. The general design of an air-to-air heat exchanger uses a series of plates, called a core, stacked vertically or horizontally.

An ideal plate has high thermal conductivity, high resistance to corrosion, an ability to absorb noises, low cost and low weight. Common plate materials include aluminum, different types of plastic sheets and advanced composites. Originally, heat exchangers used aluminum plates. Problems occurred with corrosion in the damp environment, created by condensation, and poor sound characteristics. Plastics solved the corrosion and some sound problems, but the conductivity did not equal that of the aluminum and the cost was higher.

Current high-technology heat exchangers use composite materials meeting all the criteria. In addition to the core, the unit consists of an insulated container, defrost controls to prevent moisture freezing on the core and fans to move the air. All heat exchangers need insulation to increase efficiency and reduce condensation formation on the outside of the unit. Different types of defrost mechanisms with sensors within the unit are available to control the defrost process. Fans move air to provide the necessary airflow and ventilation rate.

Counter-flow heat exchangers consist of a core of flat plates. As Figure 6 shows, air enters either end of the exchanger. Heat transfers through the plates to the cooler air. The longer the air runs in the unit, the greater the heat exchange. The percentage of heat recovery is the efficiency of the unit. Efficiencies usually range around 80 percent. Generally, these units are long, shallow and rectangular, with ducts at either of the long ends.

Cross-flow heat exchangers also use flat plates, but the air flows at right angles Figure 7. The units have a smaller footprint and may even fit in a window, but lose some of the counter-flow efficiency.

Efficiencies typically do not exceed 75 percent. These units are often cube-shaped with all connections on one face of the cube. The vast majority of heat exchangers used in residential applications use the cross-flow design. Figure 7. Cross-flow heat exchanger: The airstreams flow at right angles to each other. RenewAire Ventilation. Choose the model that would best fit your particular needs. Characteristics such as space available for installation, exchange rate needed and the desired efficiency should be considered.

Unfortunately, nearly every manufacturer has different ways of reporting these numbers. For example, ventilation rates depend on the resistance to airflow.

A fan with an airflow rate of cubic feet per minute cfm actually may produce this flow only at very low pressures.

Likewise, a unit may have a stated efficiency of 85 percent, but may not be better than a unit with an 80 percent efficiency, depending on the test temperature. The tests are used to generate an air-to-air heat exchanger specification sheet. This sheet, shown in Figure 8 , normalizes exchangers to a given set of pressures and temperatures, enabling efficiencies and airflow rates to be compared across models.

The ventilation performance numbers relate the airflow rates to a given pressure, while the energy performance relates a set of given outdoor temperatures to different types of efficiencies. Figure 8. July Addenda f to Standard April Addenda e to Standard April Addenda b to Standard January Interpretation IC of September Addenda d to Standard September Addenda v to Standard February Interpretation IC Standard March Errata to Standard February Errata to Standard Simple right?

No chance. It gets complicated because sometimes the best strategies to keep water vapor out also trap water vapor in. This can be a real problem if the assemblies start out wet because of rain or the use of wet materials.

It gets even more complicated because of climate. In general water vapor moves from the warm side of building assemblies to the cold side of building assemblies. This is simple to understand, except we have trouble deciding what side of a wall is the cold or warm side. Logically, this means we need different strategies for different climates. We also have to take into account differences between summer and winter.

Finally, complications arise when materials can store water. This can be both good and bad. A cladding system such as a brick veneer can act as a reservoir after a rainstorm and significantly complicate wall design.

Alternatively, wood framing or masonry can act as a hygric buffer absorbing water lessening moisture shocks. What is required is to define vapor control measures on a more regional climatic basis and to define the vapor control measures more precisely. Part of the problem is that we struggle with names and terms. We have vapor retarders, we have vapor barriers, we have vapor permeable we have vapor impermeable, etc.

What do these terms mean? It depends on whom you ask and whether they are selling something or arguing with a building official. In an attempt to clear up some of the confusion the following definitions are proposed:. The current International Building Code and its derivative codes defines a vapor retarder as 1. In other words the current code definition of a vapor retarder is equivalent to the definition of a Class II Vapor Retarder proposed by the author.

Continuing in the spirit of finally defining terms that are tossed around in the enclosure business. It is also proposed that materials be separated into four general classes based on their permeance again nothing new, this is an extension of the discussion in ASHRAE Journal, February 02 — Moisture Control for Buildings :. The following building assembly recommendations are climatically based see Side Bar 1 and are sensitive to cladding type brick or stone veneer, stucco and structure concrete block, steel or wood frame, precast concrete.

The recommendations apply to residential, business, assembly, and educational and mercantile occupancies. The recommendations do not apply to special use enclosures such as spas, pool buildings, museums, hospitals, data processing centers or other engineered enclosures such as factory, storage or utility enclosures.

Avoidance of using vapor barriers where vapor retarders will provide satisfactory performance. Avoidance of using vapor retarders where vapor permeable materials will provide satisfactory performance.

Thereby encouraging drying mechanisms over wetting prevention mechanisms. Avoidance of the installation of vapor barriers on both sides of assemblies — i. Avoidance of the installation of vapor barriers such as polyethylene vapor barriers, foil faced batt insulation and reflective radiant barrier foil insulation on the interior of air-conditioned assemblies — a practice that has been linked with moldy buildings Lstiburek, Avoidance of the installation of vinyl wall coverings on the inside of air-conditioned assemblies — a practice that has been linked with moldy buildings Lstiburek, Each of the recommended building assemblies were evaluated using dynamic hygrothermal modeling.

The moisture content of building materials that comprise the building assemblies all remained below the equilibrium moisture content of the materials as specified in ASHRAE P under this evaluation approach.

WUFI was used as the modeling program Kunzel, More significantly, each of the recommended building assemblies have been found by the author to provide satisfactory performance under the limitations noted. Satisfactory performance is defined as no moisture problems reported or observed over at least a year period.

This wall assembly has all of the thermal insulation installed to the interior of the vapor barrier and therefore should not be used in cold regions or colder. It is also a durable assembly due to the block construction and the associated moisture storage hygric buffer capacity. The wall assembly does contain water sensitive cavity insulation except where spray foam is used and it is important that this assembly can dry inwards — therefore vapor semi impermeable interior finishes such as vinyl wall coverings should be avoided.

In this wall assembly the vapor barrier is also the drainage plane and air barrier. This assembly has all of the thermal insulation installed on the interior of the concrete block construction but differs from Figure 2 since it does not have a vapor barrier on the exterior. The assembly also does not have a vapor barrier on the interior of the assembly. It has a large moisture storage hygric buffer capacity due to the block construction. The rigid insulation installed on the interior should ideally be non-moisture sensitive and allow the wall to dry inwards — hence the recommended use of vapor semi permeable foam sheathing.

Note that foam sheathing faced with aluminum foil or polypropylene skins would also be acceptable provided only non-moisture sensitive materials are used at the masonry block to insulation interface. The drainage plane in this assembly is the latex painted stucco rendering. A Class III vapor retarder is located on both the interior and exterior of the assembly the latex paint on the stucco and on the interior gypsum board. This assembly is a variation of Figure 3.

It also has all of the thermal insulation installed on the interior of the concrete block construction but differs from Figure 3 due to the addition of a frame wall to the interior of the rigid insulation. This assembly also does not have a vapor barrier on the exterior. Applicability — all hygro-thermal regions. This wall is a variation of Figure 1 — but without the moisture storage or hygric buffer capacity. This wall is also a durable wall assembly. It is constructed from non-water sensitive materials and has a high drying potential inwards due to the frame wall cavity not being insulated.

It can also be constructed virtually anywhere. In cold climates condensation is limited on the interior side of the vapor barrier as a result of installing all of the thermal insulation on the exterior side of the vapor barrier which is also the drainage plane and air barrier in this assembly.

In hot climates any moisture that condenses on the exterior side of the vapor barrier will be drained to the exterior since the vapor barrier is also a drainage plane. This wall assembly will dry from the vapor barrier inwards and will dry from the vapor barrier outwards.

This wall is a flow through assembly — it can dry to both the exterior and the interior. It has a Class III vapor retarder on the interior of the assembly the latex paint on the gypsum board. The cavity behind the brick veneer should be at least 2 inches wide source: Brick Institute of America and free from mortar droppings. The drainage plane in this assembly is the building paper or building wrap. The air barrier can be any of the following: the interior gypsum board, the exterior gypsum wallboard or the exterior building wrap.

This wall is a variation of Figure 6. The exterior gypsum sheathing becomes the drainage plane. As in Figure 6 this wall is a flow through assembly — it can dry to both the exterior and the interior.

The air barrier in this assembly can be either the interior gypsum board or the exterior gypsum sheathing.