Air return duct

Air return duct systems can be configured in two ways: each room can have a return duct that sends air back to the heating and cooling equipment, or return grills can be located in central locations on each floor. For the latter case, either grills must be installed to allow air to pass out of closed rooms, or short "jumper ducts" can be installed to connect the vent in one room with the next, allowing air to flow back to the central return grilles. Door undercuts help, but are usually not sufficient for return airflow.

You can perform a simple check for adequate return air capacity by doing the following:

1. Close all exterior doors and windows
2. Close all interior room doors
3. Turn on the central air handler
4. "Crack" interior doors one by one and observe if the door closes or further opens "on its own." (Whether it closes or opens will depend on the direction of the air handler-driven air flow.) Rooms served by air-moved doors have restricted return air flow and need pressure relief as described above

DESIGNING AND INSTALLING NEW DUCT SYSTEMS

DESIGNING AND INSTALLING NEW DUCT SYSTEMS

Efficient and well-designed duct systems distribute air properly throughout your home without leaking to keep all rooms at a comfortable temperature. The system should provide balanced supply and return flow to maintain a neutral pressure within the house.

Even well sealed and insulated ducts will leak and lose some heat, so many new energy-efficient homes place the duct system within the conditioned space of the home. The simplest way to accomplish this is to hide the ducts in dropped ceilings and in corners of rooms. Ducts can also be located in a sealed and insulated chase extending into the attic or built into raised floors. In both of these latter cases, care must be taken during construction to prevent contractors from using the duct chases for wiring or other utilities.

In either case, actual ducts must be used -- chases and floor cavities should not be used as ducts. Regardless of where they are installed, ducts should be well sealed. Although ducts can be configured in a number of ways, the "trunk and branch" and "radial" supply duct configurations are most suitable for ducts located in conditioned spaces.

living area.

• living area.
• Be sure a well-sealed vapor barrier exists on the outside of the insulation on cooling ducts to prevent moisture condensation.
• If you have a fuel-burning furnace, stove, or other appliance or an attached garage, install a carbon monoxide (CO) monitor to alert you to harmful CO levels.
• Be sure to get professional help when doing ductwork. A qualified professional should always perform changes and repairs to a duct system.

MINOR DUCT REPAIR TIPS

Although minor duct repairs are easy to make, qualified professionals should seal and insulate ducts in unconditioned spaces to ensure the use of appropriate sealing materials.

MINOR DUCT REPAIR TIPS

• Check your ducts for air leaks. First, look for sections that should be joined but have separated and then look for obvious holes.
• Duct mastic is the preferred material for sealing ductwork seams and joints. It is more durable than any available tape and generally easier for a do-it-yourself installation. Its only drawback is that it will not bridge gaps over ¼ inch. Such gaps must be first bridged with web-type drywall tape or a good quality heat approved tape.
• If you use tape to seal your ducts, avoid cloth-backed, rubber adhesive duct tape -- it tends to fail quickly. Instead, use mastic, butyl tape, foil tape, or other heat-approved tapes. Look for tape with the Underwriters Laboratories (UL) logo.
• Remember that insulating ducts in the basement will make the basement colder. If both the ducts and the basement walls are not insulated, consider insulating both. Water pipes and drains in unconditioned spaces could freeze and burst if the heat ducts are fully insulated be-cause there would be no heat source to prevent the space from freezing in cold weather. However, using an electric heating tape wrap on the pipes can prevent this. Check with a professional contractor.
• Hire a professional to install both supply and return registers in the basement rooms after converting your basement to a 

Your air ducts are one

Your air ducts are one of the most important systems in your home, and if the ducts are poorly sealed or insulated they are likely contributing to higher energy bills.

Your home's duct system is a branching network of tubes in the walls, floors, and ceilings; it carries the air from your home's furnace and central air conditioner to each room. Ducts are made of sheet metal, fiberglass, or other materials.

Ducts that leak heated air into unheated spaces can add hundreds of dollars a year to your heating and cooling bills. Insulating ducts in unconditioned spaces is usually very cost-effective. If you are installing a new duct system, make sure it comes with insulation.

Sealing your ducts to prevent leaks is even more important if the ducts are located in an unconditioned area such as an attic or vented crawlspace. If the supply ducts are leaking, heated or cooled air can be forced out of unsealed joints and lost. In addition, unconditioned air can be drawn into return ducts through unsealed joints

VENTILATION FOR COOLING

VENTILATION FOR COOLING

Ventilation for cooling is the least expensive and most energy-efficient way to cool buildings. Ventilation works best when combined with techniques to avoid heat buildup in your home. In some climates, natural ventilation is sufficient to keep the house comfortable, although it usually needs to be supplemented with spot ventilation, ceiling fans, window fans, and—in larger homes—whole-house fans.

Ventilation is not an effective cooling strategy in hot, humid climates where temperature swings between day and night are small. In these climates, however, natural ventilation of your attic (often required by building codes) will help to reduce your use of air conditioning, and attic fans may also help keep cooling costs down

WHOLE-HOUSE VENTILATION

WHOLE-HOUSE VENTILATION

The decision to use whole-house ventilation is typically motivated by concerns that natural ventilation won't provide adequate air quality, even with source control by spot ventilation. Whole-house ventilation systems provide controlled, uniform ventilation throughout a house. These systems use one or more fans and duct systems to exhaust stale air and/or supply fresh air to the house.

There are four types of systems:

• Exhaust ventilation systems work by depressurizing the building and are relatively simple and inexpensive to install.
• Supply ventilation systems work by pressurizing the building, and are also relatively simple and inexpensive to install.
• Balanced ventilation systems, if properly designed and installed, neither pressurize nor depressurize a house. Rather, they introduce and exhaust approximately equal quantities of fresh outside air and polluted inside air.
• Energy recovery ventilation systems provide controlled ventilation while minimizing energy loss. They reduce the costs of heating ventilated air in the winter by transferring heat from the warm inside air being exhausted to the fresh (but cold) supply air. In the summer, the inside air cools the warmer supply air to reduce ventilation cooling costs.

Natural ventilation

Natural ventilation is unpredictable and uncontrollable—you can't rely on it to ventilate a house uniformly. Natural ventilation depends on a home's airtightness, outdoor temperatures, wind, and other factors. During mild weather, some homes may lack sufficient natural ventilation for pollutant removal. During windy or extreme weather, a home that hasn’t been air sealed properly will be drafty, uncomfortable, and expensive to heat and cool.

SPOT VENTILATION

Spot ventilation can improve the effectiveness of natural and whole-house ventilation by removing indoor air pollution and/or moisture at its source. Spot ventilation includes the use of localized exhaust fans, such as those used above kitchen ranges and in bathrooms. ASHRAE recommends intermittent or continuous ventilation rates for bathrooms of 50 or 20 cubic feet per minute and kitchens of 100 or 25 cubic feet per minute, respectively

VENTILATION STRATEGIES

VENTILATION STRATEGIES

There are three basic ventilation strategies—natural ventilation, spot ventilation, and whole-house ventilation.

NATURAL VENTILATION

Natural ventilation is the uncontrolled air movement in and out of the cracks and small holes in a home. In the past, this air leakage usually diluted air pollutants enough to maintain adequate indoor air quality. Today, we are sealing those cracks and holes to make our homes more energy-efficient, and after a home is properly air sealed, ventilation is necessary to maintain a healthy and comfortable indoor environment. Opening windows and doors also provides natural ventilation, but many people keep their homes closed up because they use central heating and cooling systems year-round

Ground source heat pumps

Ground source heat pumps All analyzed heat pump systems are installed in German single family houses with floor heating. The heat pump is more or less monovalent, only a very small amount of backup heat has been used during the year of measurements. The heat pumps in the study were all  installed in new built houses during the years 2004-2008.  The data used for the SPF calculations are based on field measurements carried out during one year, with one exception the SPF for site no. 1 is based on data measured from January to August.
The calculations of SPF’s are based on the field measurements data from the Fraunhofer study. In the data we have received from the Fraunhofer study the total energy consumption for the heat pump system and its components is presented as well as the energy consumption divided into energy used for space heating and energy used for production of domestic hot water

In this project

In this project we have not been able to evaluate exactly how these allocations have been made. For some of the studied installation sites a part (up to 20%) of the total electricity consumption has been allocated neither to space heating nor to the domestic hot water production. This is mainly the case for the electricity consumption. For the heat produced no energy gap is seen between the total energy production and the energy divided into space heating and domestic hot water.  
The calculated SPF’s in the study are based on the energy allocated to the space heating only, this in order to make the results comparable to the results from the calculation models in prEN14825 and Lot 1, which not include the production of domestic hot water.
Air to air heat pumps The field measurement of the air to air heat pumps is carried out in single family houses located in the Borås area of Sweden. All houses in the study have electricity driven radiators for back up heating.  The field measurements are based on SP method 1721. From the field measurements SPF2 and SPF3 has been calculated as described below.

The electricity consumed

The electricity consumed by the heat pump, WHP, is measured continually while the produced space heating is measured at five “performance tests” done at different outdoor temperatures. During the performance tests the heating capacity of the heat pump is measured during stable conditions and is thereby not including any defrost period. Therefore the calculated COP for each test point is based on data from only a part of the operating cycle.  
The total amount of heat produced during the total measuring period needs to be calculated based on the five performance tests. The calculations are made as follows

Ground source heat p

Ground source heat pumps When using prEN14825, data according to Table 13 has to be filled in. The chosen climate, “average” gives that Tdesign is -10°C. Tbivalent is the outdoor temperature where the capacity of heat pump covers the heat demand of the house. It is set to -10°C, to make the heat pump monovalent, like in the field study. TOL, the operation limit temperature, is set to -25°C. This temperature declares where the heat pump no longer can operate. The model calculates Pdesign as a result of Tbivalent and is the heat demand of the house at Tdesign.