Remodel Project: Weatherization

Air sealing, insulation improvements, and equipment upgrades save energy dollars

Tuning up a house's performance can be quick and relatively inexpensive

Weatherization is an opportunity to improve energy efficiency without extensive modifications to the structure of the house. It should involve a whole-house systems approach that considers energy efficiency, combustion safety, moisture management and building durability.

Test for leaks, make improvements, then test again.

A whole-house systems approach to home performance generally includes a battery of before-and-after tests that check for air leakage and measure the performance of the heating, cooling and ventilation systems. Hiring a home energy auditor is a good first step for evaluating the performance of a house. An auditor will typically use a blower door, Duct BlasterCalibrated air-flow measurement system developed to test the airtightness of forced-air duct systems. All outlets for the duct system, except for the one attached to the duct blaster, are sealed off and the system is either pressurized or depressurized; the work needed by the fan to maintain a given pressure difference provides a measure of duct leakage. and infrared camera, among other tools, both to quantify and qualify the energy wasting areas of a home. After the testing, the remediation work begins, and when it is finished, the auditor comes back to retest. The results of his second visit tells you how well the improvements are working to save energy. (For more information on blower-door testing, see "Blower Door Basics.")

Air sealing is the most important
Contrary to what some homeowners might have read or been lead to believe, replacememt windows and more insulation are not the first steps toward a more efficient house. Before any other improvements are made, air leaks must be sealed. Adding insulation to a very leaky house is counterproductive, and it makes it harder to find the leaks in the future with all the new insulation piled on top.

Will it take more than weatherizing to make the house efficient?
Some houses may not be worth energy efficiency improvements until structural problems or serious site or plumbing problems are addressed--problems that may be beyond the expertise of a weatherization contractor. Concerns may include mold in a bathroom that doesn’t have a fan or an operable window or old windows that won’t are stuck or won’t close completely; serious water leaks in the basement; or weakened foundations or structural framing.

Informed homeowners use less energy
Some energy problems aren’t directly related to the building but to the people who live there. If homeowners leave incandescent lights on 24 hours a day, won’t use exhaust fans in bathrooms and the kitchen or leave windows open in winter, homeowner education may be just as important as anything else.

A Weatherization case study:

Case Study

First evaluate, then remediate

Comfort and high energy costs were the problem

The Manuses' home suffered from a variety of common problems, including an uneven heating system that left them uncomfortable on cold winter days, and their energy costs were particularly high given the house’s moderate square footage and San Francisco’s temperate climate.

Prior to the renovation, monthly energy bills averaged $350, even with the thermostat below 65°F on cold days. By setting priorities based on an initial comprehensive home-performance evaluation, Sustainable Spaces created a phased plan to maximize the client’s return on investment in dollars as well as in health and comfort. The Manus family now has a comfortable home with clean air and significantly lower energy bills.

Design Notes

Reduce the heating load, then make other reductions

To address the homeowners’ goals and concerns in a practical, cost-effective manner, Sustainable Spaces started with a detailed performance inspection, including insulation, outdoor air infiltration, duct leakage, heating and cooling load and systems, moisture issues, water heating, lighting, appliances, and general durability, to evaluate the home as a system.

Based on the findings, the team prescribed a list of priorities targeting those issues that resulted in uncomfortable rooms, unhealthy air, and wasted energy. The project started with building fundamentals—envelope-sealing and weatherization, duct-system redesign and replacement, additional attic insulation, and a lighting retrofit.

By first reducing the home’s energy load, the team significantly reduced the size of major system improvements, including a new hydronic air handler and air filtration system, a new high-efficiency hot water heater (now the home’s primary heat source for domestic hot water and space heating), and a demand recirculation pump for convenience and water conservation.

Using energy modeling software to determine the amount and balance of airflow to each room and to design ductwork to ensure that the system is properly balanced, the team took the guesswork out of making the home comfortable and efficient. Finally, after completing remediation, every step was tested and commissioned to ensure that the home performed as designed.


Key systems

General Design and Construction
*Home engineered for balanced, comfortable heating
*Air quality improved through duct and envelope sealing
*Airborne pollutants extracted with high-efficiency filtration
*Energy consumption reduced through heating and electrical load reduction

Building EnvelopeExterior components of a house that provide protection from colder (and warmer) outdoor temperatures and precipitation; includes the house foundation, framed exterior walls, roof or ceiling, and insulation, and air sealing materials.
*Blower-door testTest used to determine a home’s airtightness: a powerful fan is mounted in an exterior door opening and used to pressurize or depressurize the house. By measuring the force needed to maintain a certain pressure difference, a measure of the home’s airtightness can be determined. Operating the blower door also exaggerates air leakage and permits a weatherization contractor to find and seal those leakage areas. to identify amount of air leakage; building envelope sealing to achieve compliance with ASHRAE 62.2A standard for residential mechanical ventilation systems established by the American Society of Heating, Refrigerating, and Air-Conditioning Engineers. Among other requirements, the standard requires a home to have a mechanical ventilation system capable of ventilating at a rate of 1 cfm for every 100 square feet of occupiable space plus 7.5 cfm per occupant. requirement for hourly fresh-air exchange
*Noninsulation contact-rated can lights replaced insulated models
*12" of blown-in cellulose installed in attic to achieve R-38 or greater insulation

HVAC(Heating, ventilation, and air conditioning). Collectively, the mechanical systems that heat, ventilate, and cool a building.
*Duct-blaster test to identify amount of duct leakage (before, 360 CFM25; after, 76 CFM25; leakage reduction of 79%)
*Total heating loadRate at which heat must be added to a space to maintain a desired temperature. See cooling load. reduced from 50,600 btuBritish thermal unit, the amount of heat required to raise one pound of water (about a pint) one degree Fahrenheit in temperature—about the heat content of one wooden kitchen match. One Btu is equivalent to 0.293 watt-hours or 1,055 joules. to 38,200 btu, a decrease of 25%
*Ducts replaced with properly designed and installed R-6 wireflex ductwork
*System engineered based on ACCA Manual J load calculations, Manual D (ducts), and Manual S (sizing of equipment)
*System commissioned to ensure airtight ducts, proper static pressure, and proper room-by-room airflow
*Existing furnace replaced with properly sized hydronic air handler
*Energy StarLabeling system sponsored by the Environmental Protection Agency and the US Department of Energy for labeling the most energy-efficient products on the market; applies to a wide range of products, from computers and office equipment to refrigerators and air conditioners. programmable thermostat
*High-efficiency air filtration system
*New high-efficiency, fast-recovery water heater with side taps for hydronic heating
*Insulated hot-water pipes
*Demand recirculation pump to conserve water and energy and reduce time for hot water delivery

*Homeowners instructed on proper usage of new equipment
*Programmed thermostat to balance comfort and efficiency


A solution for heat and hot water

The homeowners originally wanted a tankless hot water heater, but their home-performance inspector recognized that large gas bills and lack of comfort and indoor air quality were their underlying concerns. Although tankless water heaters can be a good fit in some situations, a systems-based approach revealed that a high-efficiency, power-vented storage water heater was more economical and appropriate for the new combined domestic hot water and space-conditioning system.


Teams and processes

Sustainable Spaces takes a holistic approach, evaluating a home’s performance as a dynamic, interdependent system in order to identify specific steps to improve indoor air quality, comfort, and energy efficiency while always keeping the homeowners’ objectives in mind. A licensed general and solar contractor specializing in home testing and building performance remediation for existing homes, Sustainable Spaces sought first to understand the owners concerns and behaviors. Combined with quantitative data about the home’s performance, this allowed Sustainable Spaces to tailor solutions to their goals, budgets, and priorities while creating an efficient, comfortable, and healthy green home.

Location: Castro Valley, California
Homeowners: Kathy and Mike Manus
General Contractor: Sustainable Spaces Inc.
Area affected: 1,800 ft2


Sustainable Spaces created a roadmap for this project based on multiple phases, focusing first on those items with the biggest impact but within the framework of the client‘s long-term goals. A phased approach fitted the Manuses’ budget while achieving measurable results. By focusing improvements on air quality, comfort and environmental impact in addition to energy savings, Sustainable Spaces was able to get buy-in from the client for more integrated solutions.



Remodeling Details


Home Performance Strategies

green points

LEED for HomesLeadership in Energy and Environmental Design. LEED for Homes is the residential green building program from the United States Green Building Council (USGBC). While this program is primarily designed for and applicable to new home projects, major gut rehabs can qualify. Weatherization, as part of a gut rehab project, may make a project eligible to earn LEED for Homes certification. Two key elements required are a quality insulation installation and good air sealing.

NGBSNational Green Building Standard Based on the NAHB Model Green Home Building Guidelines and passed through ANSI. This standard can be applied to both new homes, remodeling projects, and additions. -Remodel Refer to the ANSIAmerican National Standards Institute. National nonprofit membership organization that coordinates development of national consensus standards. Accreditation by ANSI signifies that the procedures used meet the Institute’s essential requirements for openness, balance, consensus, and due process. standard and follow the appropriate path based on conditioned floor area involved in the remodeling or addition project and the year in which the original home was built. NGBS



Building envelopeExterior components of a house that provide protection from colder (and warmer) outdoor temperatures and precipitation; includes the house foundation, framed exterior walls, roof or ceiling, and insulation, and air sealing materials.
Conduct blower-door tests before and after the project, along with room-to-room pressurization tests. Perform air-sealing work in the basement and attic. Use infrared imaging to find places where insulation is inadequate. If required, weatherstrip doors and windows. If required, add insulation in the attic, using formaldehydeChemical found in many building products; most binders used for manufactured wood products are formaldehyde compounds. Reclassified by the United Nations International Agency for Research on Cancer (IARC) in 2004 as a “known human carcinogen."-free insulation.

HVAC(Heating, ventilation, and air conditioning). Collectively, the mechanical systems that heat, ventilate, and cool a building.
In houses that have forced-air heating systems, test ducts for air tightness. Check the operation of the combustion equipment for efficiency and combustion safety. Install smoke and carbon monoxide alarms if they’re not already present.

Replace incandescent bulbs with compact fluorescents.

Insulate hot water pipes and, if necessary, the water heater.

Image Credits:

  1. Julia Jandrisits/REGREEN
  2. Matt Golden/REGREEN
  3. Mark Piepkorn/REGREEN
  4. Peter Yost/REGREEN
Tags: , , , ,
Nov 3, 2009 6:46 AM ET

Power Tools
by Dave Tool

Absolutely make sure you seal those air leaks first and foremost. For some reason homeowners I work with tend to discount the amount of heat lost through tiny cracks and crevices without realizing these miniature leaks can completely undo all the combined weatherizing efforts you've put in to the rest of the house!

Register for a free account and join the conversation

Get a free account and join the conversation!
Become a GBA PRO!