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Windows and Skylights

Fenestration products in your home consist of windows, window films, skylights, glazed doors, and dynamic glazing and have a significant impact on energy use and efficiency. Their size, orientation, and type are all factors taken into account while determining Title 24 compliance. Fenestration will also affect the operation of your lighting and HVAC system.

Windows and Glazed Doors: Windows are defined as a vertical fenestration product composed of a frame and sash component which holds one or more sections of glazing. Its performance is measured by U-factor and its solar heat gain coefficient (SHGC). A glazed door is an exterior door with 25% or more being glazed area. Glazed doors are modeled as windows and are required to meet the same U-factor and SHGC requirements.

Skylights and Tubular Daylight Devices: Skylights and tubular daylight devices (TDD) can be an excellent source of passive solar heating and both direct and indirect lighting. These products do not have the same thermal properties as windows and can be prone to both greater heat loss and solar heat gain depending on the season. 

Example of glazing in architecture


Insulation is one of the most cost efficient ways to improve the energy usage of your home. In addition to requiring no maintenance, insulation provides substantial sound control and improves indoor comfort. Maximizing insulation levels from the beginning is far cheaper and easier than adding more later. Innovative building products and continually advancing construction techniques are key tools for designers and builders who recognize the value of high performance, efficient buildings. There are four types of insulation used in residential building - batt and blanket, loose-fill, spray polyurethane foam (SPF), and rigid insulation. Which type is used will vary depending on design and type of construction.

Batt and Blanket: Made of mineral fiber and mineral wool, animal wool or cotton based product, or cellulose material. Batt and blanket insulation is used within walls, above ceilings, below roofs, and below floors. Size and thickness determine the products R-value (inverse of U-factor) and are available either with facings to help with installation or unfaced to allow easy installation into framed cavities.

Loose-Fill Insulation: This type of insulation, comprised of similar products as batt and blanket, is installed by blowing it into a wall cavity or attic. Loose-fill insulation can be an effective way to deal with areas around pipes, electric cables, junction boxes, or other irregularities. Unlike other types of insulation that have set R-values and pre-formed dimensions, loose-fill insulation efficiency is determined by its installed thickness and density. 

Spray Polyurethane Foam (SPF): SPF insulation is sprayed through a nozzle into walls, roofs, ceilings, and floor cavities. It is a two-component reactive system creating a liquid-foamed thermoset plastic. Mixed with blowing agents, surfactants, and catalysts it develops a cellular structure before the mixture cures. SPF can be manufactured to provide specific properties such as fire resistance, density, compressive strength, and R-value.

Rigid Insulation: Made from fiberglass, mineral wool, polyurethane, polyisocyanurate, extruded polystyrene, or expanded polystyrene. This type of insulation varies in thickness with some variations providing up to R-6 per inch. It's variety of uses include:

  • Above-roof decks

  • Exterior walls

  • Basement walls

  • Cathedral ceilings

  • Perimeter insulation at concrete slab edges

  • Insulate special framing installations

Batt insulation being installed in wall framing

Heating, Ventilation, and Air Conditioning (HVAC)

All residential buildings must be designed and constructed in compliance with the mandatory measures of Title 24, Part 6. Mandatory measures relating to HVAC systems are primarily focused on meeting minimum equipment efficiencies, required controls, design standards, and quality of construction/installation. It is important to note however that some minimum equipment requirements may be higher than the mandatory measures to ensure they comply with the necessary prescriptive or performance methods.

How do I decide on an HVAC system type?

The most basic considerations when choosing an HVAC system are available fuel types, equipment location, and number of conditioned zones. It is important to consider both initial and operating costs, reliability, noise, and temperature control (variation) of conditioned rooms.

Modern wall HVAC thermostat
Outdoor HVAC condenser

Common Heating Systems

Split System Gas Furnace - The most common heating/cooling system for residential buildings. This system is an indoor unit with a fan and gas furnace heat exchange connected to a duct system that distributes warm air. Cooling can be added to this system easily by installing a cooling coil connected to an outdoor condensing unit. Benefits of this type of HVAC system are low operating costs, easy cooling integration, and straightforward compliance.

Split System Electric Heat Pump - Very similar to the gas furnace split system except there's no furnace heating coil. Additionally, the refrigerant cooling coil also serves as a heating coil through a reversing valve located in the outdoor unit. These systems typically include a backup electric resistance heating coil due to decreased heating capacity during low outdoor temperatures. Where gas isn't available as a fuel source a split system electric heat pump can be a relatively economic choice. Like the gas furnace, demonstrating compliance is generally straight forward and can comply prescriptively. 

Ductless Mini-Split Heat Pump -  These systems consist of an outdoor condensing unit connected by refrigerant lines to one or more fan coil units located inside the home. All indoor units include a heat pump coil and fan and can be individually set which helps temperature control. No duct system is used. While generally these systems provide good energy efficiency, their performance is significantly degraded during cold outdoor air temperatures (below 30F - 40F).

Ground Source Heat Pump - A heat pump system in which heat is either drawn from, or routed through, a water loop that circulates through ground loops. This keeps the water loop somewhat insulated from outdoor temperatures and allows the heat pump to operate with good efficiency year round. There are high startup costs associated, however, and installation is typically limited to new construction.

Baseboard Electric - When using baseboard electric heating, convectors in each room are heated by electric resistance. No fans are used, so air cleaning and circulation are not available. Additionally, electric resistance heat requires performance compliance as it isn't allowed prescriptively. Very low installation costs are a benefit, but under higher heating loads operating costs can become very expensive.


Electric Resistance Central Furnace - Similar to the gas furnace split system with the exception of the heating coil being heated by electric resistance. These systems can have very high heating costs and are typically only appropriate with low heating loads. Like baseboard electric heaters, performance compliance is necessary. Initial cost is typically low, and a cooling system can be easily integrated.

Radiant Hydronic System -  Instead of using convectors as hot water baseboard systems do the hot water is circulated through tubing embedded in the floor. This system cannot be integrated with a cooling system and does not provide air cleaning. When gas is used to heat the water radiant floors have low operating costs and provide very good comfort. Radiant Hydronic Systems can comply prescriptively, and compliance is straightforward.

Water lines of a radiant hydronic system being installed in floor

Radiant Hydronic System

Common Cooling Systems

While there is a variety of residential cooling system types the most used two are direct expansion cooling and evaporative cooling. Most common is direct expansion cooling -  typically found as part of a split system, though also available in ductless mini split systems.

Central Ducted Split Systems - The most common residential cooling system. This option relies on the fan located in the central air handler or heating system to move air through the cooling coil and distribute it throughout the duct system. These systems comply prescriptively and are relatively straightforward.

US Census Data Documenting Home Heating Fuel by Decade of Cosntruction

Ductless Mini-Splits - These systems can be configured to provide only cooling or both heating and cooling. Ductless mini-split systems utilize one or more outdoor condensing units connected by refrigerant lines to fan coil units installed throughout the home. Good performance, easy compliance, and potential space saving without the duct system make them an increasingly popular choice.

Evaporative Cooling Systems - Water evaporation is used to cool the air being distributed through ducting by this system. Since no electric cooling is necessary operating costs tend to be lower, with the tradeoff being increased water consumption. 

Excerpted from the CEC Title 24 energy compliance manual

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