Table of Content
- Installing A Whole House Fan
- Evaluating Ventilation Systems for Existing Homes
- Technology Solutions Case Study: Selecting Ventilation Systems for Existing Homes
- Vent Right and Then? Mechanical Ventilation, Dehumidification, and Energy Use in Humid Climates
- Whole House Ventilation Strategies for Existing Homes
- Residential Energy Dynamics
As with all ventilation systems, it’s important to measure the delivered airflows and make sure they meet specifications or requirements. Measuring flow rates at each register is the only practical way to check system balancing. In Florida, for example, air inside conditioned homes is generally cool and dry.
Joints in the duct system should be sealed with mastic, and any ducts located outside of conditioned space (e.g., the attic) should be insulated to prevent condensation of the humid exhaust air. The duct system provides a pathway through which heated or cooled air is distributed from a central air handler throughout the house. However, leaky ducts that run through unconditioned spaces can draw in and distribute contaminants from attics, garages, and crawlspaces. Leaky ducts can also affect pressure differences inside the home that can impact combustions safety and energy efficiency or result in pushing contaminants from one space to another within the home. For these reasons, forced air heating and cooling systems should only be used for ventilation if the ducts do not leak. Supplemental dehumidification is often necessary for dwellings in humid climates.
Installing A Whole House Fan
With respect to summertime operation, ERVs seem to perform best during peak outdoor conditions and lose efficiency during low-temperature, high-humidity conditions. The fans are set to run continuously or intermittently on timer controls. Because an energy-recovery ventilator transfers some of the moisture from the exhaust air to the usually less humid incoming winter air, the humidity of the house air stays more constant. This also keeps the heat exchanger core warmer, minimizing problems with freezing.
For exact code language, refer to the applicable code, which may require purchase from the publisher. While we continually update our database, links may have changed since posting. Right - After installing the EPDM gasket around the HRV duct, first the lower edge, then the sides, then the top of the gasket are taped; 12 of 14. Right - After installing the EPDM gasket around the HRV duct, first the lower edge, then the sides of the gasket are taped; 11 of 14.
Evaluating Ventilation Systems for Existing Homes
Ducts bringing outdoor air through conditioned spaces should be insulated. Motorized dampers—which open to allow outdoor air in and close when the ventilation quotas have been met—are often available as part of a CFIS package or kit. If a different sized damper is needed, motorized dampers can certainly be acquired separately.
These controllers are available as discrete components, but many are also available as part of a kit that includes a controller, a motorized damper, and a transformer. Make sure the device used is compatible with the existing air handler and control system. If a blower door test is done on a single-family home, however, it’s likely this ventilation flow rate can be reduced.
Technology Solutions Case Study: Selecting Ventilation Systems for Existing Homes
The cost for installing these duct systems is often a large part of total system cost. To help address this challenge, some manufacturers have introduced local ERVs. Figure 8 shows such a unit installed in a ceiling in a manner somewhat similar to a bathroom exhaust fan. The unit requires two outdoor air ducts , but the unit exhausts directly from and supplies directly to the room below. Compared to conventional ERVs, this system can dramatically simplify installation and reduce costs; however, outdoor air is not distributed throughout the home but only to the room or area in which the local ERV is located. Also, heat recovery is only moderately efficient and these systems change to exhaust-only operation in cold weather.
Increasing numbers of jurisdictions continue to adopt requirements for mechanical ventilation for new dwellings. The latest versions of ASHRAE Standard 62.2 and local codes provide the minimum ventilation rate for a particular dwelling unit. The 2015 IMC, which covers most multifamily dwelling units , requires all occupiable spaces to have natural or mechanical ventilation. It also requires mechanical ventilation in dwelling units with an air infiltration rate of less than 5 ACH50 when tested with a blower door (described in detail in Strategy 1.4).
= Fresh Air Balanced System
Rules-of-thumb fail with more complex installations requiring ceiling, wall, or floor removal, construction of chases, refinishing, etc. Thermal energy required to condition outdoor air introduced into the space. Further information, including details on calculating ventilation rates, can be found in the Solution Center guide Whole-House Ventilation for New Homes and in the Compliance section of this guide. Assess existing HVAC systems and ductwork – especially if new ventilation equipment will be integrated with the existing HVAC system. In this report, BSC seeks to research and report on the field monitoring of the performance of in-situ supplemental dehumidification systems in low-energy, high performance, homes in a hot-humid climate.
Duct runs should be as short and as straight as practical to provide unrestricted airflow. Exhaust ducts should always terminate outdoors—never in an attic, basement, or crawlspace, like the exhaust duct shown in Figure 3, which ends near an attic vent grille but not outside. If possible, measure the flow rate at the outdoor termination as well.
Balanced ventilation systems, if properly designed and installed, neither pressurize nor depressurize your home. Rather, they introduce and exhaust approximately equal quantities of fresh outside air and polluted inside air. Supply ventilation systems use a fan to pressurize your home, forcing outside air into the building while air leaks out of the building through holes in the shell, bath, and range fan ducts, and intentional vents .
Sensors and controls that trigger closure of outdoor air intakes during periods of high humidity are recommended in very humid climates. Similarly, sensors and controls that automatically trigger closure of outdoor air intakes or enable manual closure during periods of poor outdoor air quality, for example if wildfires are occurring nearby, are also recommended. Similarly, sensors and controls that automatically trigger closure of outdoor air intakes or enable manual closure during periods of poor outdoor air quality, for example, if wildfires are occurring nearby, are also recommended. ENERGY STAR-rated exhaust fans are recommended for most applications; the most obvious benefit of these fans is lower energy consumption. ENERGY STAR requirements for bathroom exhaust fans call for fans to deliver a minimum of 2.8 cfm/Watt.
A qualified HVAC contractor should install the controller, ducts, dampers, and other components. The location of the duct run, connection to the return plenum, and location of the outdoor air intake should be planned beforehand. Occupancy sensors and humidity sensors can be used to turn on fans or to boost fans into high speed when higher exhaust flow rates are desired.
That’s right – install the fan, use it, and if you not satisfied – we will take it back. Right – Holes were drilled into the I joists between floors to run the small-diameter HRV ducts. Controls with carbon dioxide and/or humidity sensors can boost speed at higher concentrations . Choices need to be made between an ERV and an HRV and equipment thermal recovery efficiency should be considered. These three strategies are illustrated in Figure 1 and described in greater detail in the section Types of Whole-House Ventilation Systems below. The next section describes factors to consider when selecting a ventilation system.
Some ventilation strategies make use of point-source or local ventilation systems to meet whole-building ventilation requirements (e.g., a bath exhaust fan running continuously). These local exhaust systems are required to remove odors and pollutants—especially water vapor—from these key areas. While exhaust fans are common in many existing homes, older and low-cost fans often perform very poorly, exhausting a very small fraction of the design flow rates and consuming a large amount of electricity. ASHRAE 62.2 offers alternative compliance paths for existing homes where local exhaust fans are impractical to install.
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