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Insulation is one of the highest payback improvements you can make to a building -- at both new construction and remodeling time. Radiant barriers are a new approach with additional heat resistant benefits.

Heat Transfer

Conduction

Direct heat flow through a solid object like a roof, wall or ceiling.

Convection

Heat movement through air that occurs when air is warmed. Warm air expands, becomes less dense and rises.

Radiation

Movement of heat rays across air spaces from one warm object to another less-warm object. Wood stoves give off radiant heat, for example.

We hear about radiant barriers in applications such as the heat shielding ceramic tiles on NASA shuttles. And the aluminum foil used on baked potatoes. Those are "radiant barriers" that keep heat in... or out.

Heating air is expensive! Cooling air is also expensive -- so it makes sense that if you don't have to condition air as much, you'll save on your utility bills.

Insulation and radiant barriers are used in buildings to keep heat in during the winter...and keep heat out during hot periods and seasons. But most buildings weren't optimized for energy efficiency in both hot and cold temperatures.

Radiant Barriers for Buildings

The bright aluminum surface of radiant barrier products provides insulation properties in two ways:

• The reflective surface reflects long wave radiant heat that strikes it -- up to 97% of all radiant heat.
• Close contact, but non-touching, allows reradiation to happen, and when you reduce the amount of heat that "gets through" the radiant barrier, you will have less convection taking place.

Read more about radiant barrier effectiveness.

Strategies for net zero energy vary by household, climate, region and housing type.

Passive House Institute

The passive house standards in Germany and Austria have demonstrated that performance and cost savings can result when peak heating loads are reduced significantly.

Building Sciences Corporation completed a comprehensive renovation of a 100 year old home that resulted in a 60% energy savings while increasing the living space by 80%. (Pettit 2008)

Energy Efficiency Strategies That Work

A deep reduction approach with comprehensive insulation and air sealing can make a conventional furnace and air circulation system unnecessary, thus using simpler technical solutions to combustion safety distribution systems, durability and indoor air quality.

A deep energy retrofit could eliminate a conventional chimney, furnace and attic ductwork and replace these building elements with a mechanical ventilation system that manages indoor air quality and moisture control.

The Canadian Mortgage Housing Corporation (CMHC) recently published a study, "Approaching Net Zero Energy in Existing Housing" and concluded that climate, housing stock, energy loads, solar gain and occupant behavior all contribute to the feasibility of reaching net zero energy use in existing homes.   With no incentive available, it is not cost effective to achieve net zero energy in most Canadian housing.

Energy Efficiency Justification

Solving problems with wet basements, radon, outdated mechanical equiment and inadequate indoor air quality can help justify energy efficiency choices.

Reducing heating loads is relatively easy.  It is more challenging to achieve deep reductions in baseloads and cooling loads which are more dependent on occupant behavior and lifestyle.  Motivated occupants are essential.

The California energy crisis of 2000-2001 resulted in a 15% reduction in electrical energy use that was primarily the result of occupant behavior, not technology.  The actions of a small number of supersavers and modest efforts by many residents were deemed responsible for the reduction.

Utility programs can substantially reduce energy use with energy efficient features such as low-e windows and building enclosure improvements that focus on reducing air infiltration and upgrading insulation performance.  Also helpful are replacement of heating nd cooling systems, duct leakage reduction, and use of other controls for electrical and cooling loads.

Community Solutions

Homeowner choices sometimes affect lifestyle choices significantly.  Possible strategies can include use of renewable energy supply or a change in the use of space or the number of people in a home.  Highly effective choices can include co-housing with efficient shared cooking, water heating, clothes washing and entertainment facilities.

Reduce the Load First

Marc Rosenbaum suggests a simple maxim, "Invest as much as you can afford to reduce the load, even if it means completing a project in phases."  These load-reducing options that can help achive optimum results are major systems such as siding and roofing. 

Choices for Thermal Comfort

Thermal comfort accounts for 25 - 80% of residential energy use.   Some of the options available include:

Community Solutions

• Comfort centers
• Cogeneration or micro-cogen
• Community thermal storage
• Community-based renewable energy supply
• Use of waste heat from industrial processes
• GHG reduction campaigns
• Feedback, benchmarking, aggregation
• Competitions and challenges
• Technical, financial and regulatory support

Behavioral Choices

• 24/7 set point adjustment or setback
• Apply comfort zone
• Change use of space with new thermal boundaries
• Adaptive comfort (clothing, surface temperature, air movement)
• Increase occupancy
• Reduce internal gains with behavioral cooling loads
• Decrease occupancy size with relocation or demolishing space

Technical Solutions with Higher Cost

• Superinsulation (walls, ceiling, floor, foundation - climate specific for R25-R80)
• Efficient windows  (U 0.1 to 0.3)
• Super air tightening  (0.2 CFM/ftx2 floor space)
• High efficiency mechanical ventilation
• Ultra high efficiency HVAC system
• Automatic movable window insulation
• Highly insulated doors

Technical Solutions with Lower Cost

• Fill cavities with insulation
• Air sealing
• Do-it-yourself superinsulation
• Seal / insulate attic ducts or eliminate ducts
• Point heat or cooling source
• High performance storm windows
• Manually controlled movable window insulation
• Reduce internal gains with technical fix of cooling loads
• Control systems to optimize comfort, indoor air quality and humidity

On-Site Renewable Energy

• Increase solar gain through windows
• Sunspace or solar buffer to reduce heat loss
• Active solar thermal
• Solar PV
• Wood heat
• Trees vegetation or other shading to reduce cooling loads

Initial results from a research study in East Tennessee shows that energy-efficient upgrades can pay off for homeowners by reducing heating costs by 35 to 65%.

"The retrofit unit provided 35% measured heating energy savings from the builder home, yet offers a package of technologies that are considered to be a reasonable upgrade for many homes in the United States," says Jeff Christian,  Department of Energy's Oak Ridge National Laboratory.

While the study focuses on improvements to existing homes new, unoccupied homes were used in order to keep the results as unbiased as possible.

The houses are typical two-story models built on insulated slabs with similar solar orientation, lot slope, wall areas, wind exposure and size.

The study uses three similar homes in the same development to gather real-world data about various energy-efficient improvements that can be made to an existing home.  The study is sponsored by the Tennessee Valley Authority and is being conducted in cooperation with researchers from the Oak Ridge National Laboratory.

Computers and instrumentation are programmed to simulate occupancy, including opening refrigerator doors, automatic clothes washing and drying, showers, lights and plug loads in all three homes. But that's where the similarities end.

The Control Home
The control or builder home was built to meet current building codes and earned a Home Energy Rating System score of 90, slightly better than a typical code-compliant home. It is equipped with two heat pumps, one for each floor, that have a total capacity of 4.5 tons.

The Retrofit House
The retrofit house includes energy-efficient upgrades that focus on the building envelope and mechanical equipment. These allowed the HVAC system to be reduced to one, three-ton heat pump located inside the conditioned envelope. The retrofit home earned a HERS rating of 66 - a better score than the builder's home.


Energy Improvements
Improvements to the home include installing

• low-E gas-filled windows
• changing all light bulbs to compact fluorescents
• replacing the ceiling insulation with spray polyurethane foam insulation on the underside of the roof deck and attic walls to make it an unvented, semi-conditioned space.

Attic-based HVAC Configurations
"An unvented attic is particularly helpful in climates where heating and cooling equipment is located in the attic," said Chris Porter, building science manager for BioBased Insulation®. "Modifying the attic to create an indirectly conditioned space helps significantly reduce energy consumption and improves mechanical equipment performance."

BioBased Insulation® donated the insulation for the study, and Endless Supply, a BioBased Insulation® certified dealer based in Ashville, NC, donated the labor to install the product.

Deep Retrofit Home
High-performance improvements to the third home made it a near zero energy home with a HERS rating of 34 and a measured space heating energy savings of 65 percent compared to the builder home.

While more extensive, some of the improvements could still be made to a deep retrofit of an existing home. They included,

• 2.5 kW solar panels,
• solar hot water heater,
• triple-layered windows with an R-value of 7,
• structurally insulated sheathing and
• BioBased Insulation® in the walls,
• R49 attic insulation with radiant barrier sheathing.
• The builder was able to downsize to one, two-ton heat pump because of the envelope improvements.

"With three houses with actual identical simulated occupancy we will have research capabilities that are world-unique," Christian said. "And the really exciting thing is that these homes will be available for research for seven years, so we will be able to replace, test and accelerate the development of even more efficient technologies."

How much do energy-efficient upgrades cost?

The upgrades included in the retrofit home cost $4 per square foot or about $9,800 more than the control home.

Upgrades to the near zero energy home cost $21 per square foot or $51,576 more than the control home.

Payback and ROI
Based simply on projected energy savings, homeowners who implement the retrofit upgrades would recoup their costs in 8.5 years.

It will take homeowners who implement the near zero energy upgrades 22 years to recoup their costs.

While the current round of results includes the heating season only, monitoring will continue during summer, and results for a full year of the homes' operation should be available this fall.

Rebates and Tax Deductions
"We're excited to be part of the study," Porter said. "Recently we've seen an increase in the number of homeowners taking advantage of the $1,500 Federal Tax deduction and other rebate programs. Many are doing upgrades similar to those found in these test houses. Even though these are only initial results, they are still very helpful in quantifying the energy savings from these retrofit options."