Heating & Cooling, Insulation & Ventilation

The greatest opportunities for energy savings come from heating and cooling your building more efficiently — and the investments pay back very fast.

Your project can be designed to use 30% less energy than typical buildings, and if you start this approach early in design, it can be built for the same initial cost. The key is integrated design – thinking about the whole building together and the way all the parts relate to each other, and how the outside environment affects mechanical systems inside. Ventilation is also an important way to provide a healthy building – and health is an investment that is always worthwhile.

Goal: Save energy through passive design

Passive design means planning out the natural heat flows through your building in advance, so that the building will stay cool when it's hot outside, and warm when it's cold.

1 Passive design
2 Natural cooling
3 Ceiling fans
3 More Insulation
3 High-efficiency equipment
3 Heat recovery
3 Alternative systems
3 Ductwork
3 Zoning
3 Radiant heat
3 Refrigerants
3 Green insulation
3 Separate ventilation
3 Alternative fireplaces

Passive design is basically free, or "cost–neutral," because it uses essential building parts you have to buy anyway — mass and windows — and freely available sunshine and wind on your site (see Site & Landscape; Windows & Doors). With the money saved by not buying expensive Heating Ventilating and Air Conditioning (HVAC) equipment, you can afford items to fine–tune your passive design to achieve superior indoor comfort that reflects the best aspects of San Mateo County's mild climate.

area one

Use passive solar design, thermal mass, and insulation to reduce space heating needs

What is this?

Passive solar design is the heating counterpart to passive cooling discussed above. South–facing windows will allow in warm winter sunshine. Thermal mass can absorb this free heat, instead of allowing it to overheat the room, and the right insulation level will prevent heat loss to the outdoors.

Why do it?

Sunshine is free but heating fuels cost money. A passive heating approach can easily replace 25% of heating fuel use; a thorough design can save 75% or more.

How to do this?

Computer building energy simulation is the best way to achieve a passive design that really works. Weather data for San Mateo County locations is combined with information about building size and orientation, windows, insulation in walls, and thermal mass to calculate what interior temperatures will be throughout the year. This approach also allows you to detect the potential for overheating in the summer and rectify it with additional shading or other techniques.

Who does this?

Architects, energy consultants, mechanical engineers.


Passive Solar Design Image

In simple passive solar design, roof overhangs, porches, trees, or awnings are arranged to allow sunshine in during winter and provide shade in summer. Building thermal mass and insulation keep the interior at a desirable temperature as outdoor conditions change.


area one

Replace air conditioning with natural ventilation and passive cooling

What is this?

Natural ventilation brings in outdoor air through windows instead of an air handling system. Passive cooling stores nighttime coolness in building "thermal mass" to offset the heat gained from building users, maintaining a comfortable temperature. In San Mateo County, air conditioning is not really necessary except in some commercial buildings. Less than 1% of the year has outdoor temperatures over 90°F in most places.

Why do it?

Comfort without air conditioning is cheaper and healthier. Heating and cooling often takes 40% of all energy used in a building, and passive design can reduce this to close to zero. Also, outdoor air from windows is free of the indoor pollutants that can accumulate in the recirculated air of conventional HVAC systems.

How to do this?

Design operable windows (ones you can open) to allow breezes in and out — and make sure they're shaded to prevent unwanted heat gains. Allow for night–ventilation of the building with windows, louvered vents, or fans, and provide adequate thermal mass (exposed concrete or extra gypsum wallboard) to hold the coolness. Balance these costs — plus operating energy savings — with the much smaller HVAC system you will need with this approach.

Who does this?

Architects, energy consultants, mechanical engineers.


area one

Use ceiling fans for comfort cooling

What is this?

Ceiling fans don't make air colder, but when a fan blows air over your skin you feel cooler anyway. A whole–building fan enables passive cooling (see above) by replacing warm daytime air with cool night air.

Why do it?

An air conditioner uses a lot of energy and requires fans and ductwork to recirculate and cool air. Ceiling and whole–building fans are easier to install and use a lot less energy. They work with the San Mateo County climate, instead of ignoring it.

How to do this?

Whole–building fans should be located at the top of the building (for multistory buildings), and installed tightly sealed. Windows or louvered vents should be located far from the fan to take in air and be able to be left open while the fan runs. The fan should be sized to provide 4–5 air changes per hour. Ceiling fan installations are only limited by ceiling height; installation requires electrical wiring and a switch.

Who does this?

Building owners, architects, mechanical engineers, electricians.


area one

Upgrade wall, floor, and ceiling insulation to exceed minimum State requirements

What is this?

Insulation prevents heat from moving through walls, ceilings and floors — it keeps warmth inside in winter and keeps heat outside in summer. California's Energy Code, often referred to as "Title 24," requires a minimum resistance rating ("R–value") of R–19 in San Mateo County (non–residential building walls can be R–11).

Why do it?

Title 24 is only a minimum standard, and an inch or two of additional insulation is often the most cost–effective way to reduce building energy use and save money.

How to do this?

Add rigid insulation board to exterior walls underneath sheathing, or use thicker insulation in cavities. In stud construction, sprayed–in insulation often has a higher R–value than conventional batt insulation, and also reduces air leakage. One inch of extruded polystyrene insulation board around foundations saves roughly three–quarters of the heat lost through the foundation in many buildings.

Who does this?

Building owners, architects, specification writers, energy consultants, contractors.


Goal: Save energy in equipment use

Building equipment heats, cools, and moves air and water. It includes heating and cooling sources (such as furnaces, boilers, or chillers), and distribution equipment (such as fans, pumps, ducts, and pipes). High efficiency equipment and well laid–out distribution systems are a good investment, paying off in reliable energy savings.

area one

Use high–efficiency equipment, including furnaces, boilers, fans, and pumps

What is this?

High–efficiency equipment does more heating, cooling, or pumping with less energy.

Why do it?

More efficient equipment saves money through reduced energy bills. Be sure to account for the future energy savings over 8–10 years when comparing a more efficient unit to a cheaper alternative. If the more efficient unit also has a longer life span (and many do), consider the replacement cost savings as well in this decision.

How to do this?

ENERGY STAR® (see Electrical) identifies efficient equipment such as boilers, furnaces, and central air conditioners. For larger buildings, write minimum efficiency levels into your contract and written specifications. Mechanical engineers should also consider the efficiency of larger equipment, including distribution piping or ductwork.

Who does this?

Architects, specification writers, mechanical engineers.


area one

Use heat recovery equipment

What is this?

Heat recovery is a way of transferring heat energy from an exhaust stream of air or water to an intake stream (or vice versa) without contaminating the two streams.

Why do it?

Heat exchange saves energy by keeping heat where you want it (indoors in winter, outdoor in summer) while still allowing air or water to enter and leave the building.

How to do this?

Install air heat recovery devices such as "heat wheels" in duct work. Use a gravity flow exchanger (GFX) for recovering heat from drainwater.

Who does this?

Building owners, mechanical engineers, subcontractors, plumbers.


area one

Use geothermal systems, cogeneration, or other alternatives for heating and cooling

What is this?

Many technologies can deliver heating and cooling more efficiently than just burning fossil fuels (for heating) or using electricity to run an air conditioner. Geothermal systems tap the earth's constant ground temperature as a source of heating and cooling for building use. Cogeneration burns gas to produce electricity and uses the waste heat locally, dramatically saving energy.

Why do it?

As energy prices climb and resources dwindle, conventional systems are becoming obsolete and incapable of delivering heating and cooling effectively. Alternatives are cost competitive and more efficient, and often can make your project an example of innovative thinking.

How to do this?

Exploring alternative technologies requires planning in advance to determine site feasibility and the availability of specialized systems and components.

Who does this?

Mechanical engineers, energy consultants, specialized manufacturers.


area one

Place ductwork within conditioned space, seal joints properly, and clean before occupancy

What is this?

Ductwork distributes air within a building, and is mainly made of large sheet metal and plastic tubes. It connects fans, furnaces, and air conditioners to air distribution and return vents.

Why do it?

Where and how ductwork is installed, and how it is maintained, have a big impact both on energy use and indoor air quality. Duct work outside of conditioned spaces (on a rooftop, in an attic or crawlspace) loses heat to the outdoors. Leaky ductwork anywhere loses heat and lets in unfiltered and dirty air. Because construction produces dust and fumes, duct cleaning should be done at the end of construction to keep building air clean.

How to do this?

Work with your mechanical engineer or subcontractor to address concerns about leakage and cleanliness. Use duct mastic (glue), instead of duct tape (which wears out) on all joints.

Who does this?

Mechanical engineers, mechanical subcontractors.


area one

Zone mechanical system for more efficient heating and cooling

What is this?

Different building areas often have different heating, cooling, and ventilation needs. Creating "zones" through more sophisticated control systems allows a mechanical system to deliver an appropriate amount of air at an appropriate temperature.

Why do it?

Zoning the mechanical system increases comfort and decreases energy use.

How to do this?

Variable air volume (VAV) systems offer the greatest flexibility for air distribution systems in large buildings. For smaller buildings, zoning can be achieved by using separate systems for separate areas; each system can then be optimized for its area's particular needs.

Who does this?

Mechanical engineers.


area one

Use radiant and hydronic systems for increased efficiency, health and comfort

What is this?

Hydronic systems circulate hot and cold water, instead of air, to heat and cool buildings. Radiant systems transfer hydronic heat to occupants through the floor or with ceiling panels.

Why do it?

Hydronic heat delivery uses pipes instead of ducts, which are smaller and so save building space. Also, adding control zones (see above) is a minor expense for hydronic systems, but costly for air systems. Radiant systems can also be more comfortable and more efficient than air–based heating and cooling.

How to do this?

Plan early for a hydronic system, since the savings on duct space (especially in dropped ceilings) can be substantial. A small air system may still be necessary to meet ventilation air requirements, although this can often be achieved with natural ventilation (see above). Radiant floors in particular require careful integration with building structural components.

Who does this?

Architects, mechanical engineers, specialized consultants and subcontractors.


area one

Use equipment without ozone–depleting refrigerants

What is this?

Most refrigerants used in air conditioners are hydrochlorofluorocarbons (HCFCs) that destroy ozone in the atmosphere; some newer models use alternatives.

Why do it?

International treaties have banned the worst ozone depleting chemicals. Most of their current replacements still deplete ozone, but at a slower rate, so using truly ozone–friendly alternatives is still important to protect the Earth from excessive UV radiation.

How to do this?

Include this requirement in project specifications and consult with your mechanical engineer or subcontractor.

Who does this?

Mechanical engineers, mechanical subcontractors


Goal: Create healthy indoor environments

Indoor air quality is affected by building materials and activities inside of buildings. Choosing materials that are non–toxic helps prevent indoor illnesses, especially among especially sensitive individuals, children, and the elderly.

area one

Use recycled–content, formaldehyde–free fiberglass insulation, cellulose insulation, or other green insulation products

What is this?

Green insulation products include fiberglass made in formaldehyde–free processes (in white batts); sprayed cellulose (shredded paper with non–toxic fire retardants); cotton batts; and hypo–allergenic foams (Icynene™, AirKrete™, and BioBase 501™ are leading examples).

Why do it?

Conventional fiberglass insulation (in pink or yellow rolled batts) contains formaldehyde, which is a known carcinogen. Not only can you keep this dangerous substance out of your house, but many alternative products are easier to install (such as cotton batting) and/or tighter sealing (such as cellulose and hypo–allergenic foams), which saves energy.

How to do this?

Alternative batt insulation products replace fiberglass directly and most contractors can handle the substitution themselves. Sprayed–in insulation usually requires a specialty subcontractor and additional jobsite preparations. Write these products into project specifications so general contractors can plan on including them.

Who does this?

Architects, specification writers, contractors, specialized subcontractors.


area one

Separate ventilation for indoor pollutant sources and provide advanced filtration to improve indoor air quality

What is this?

Some indoor materials and activities generate toxic air pollutants, especially copiers and other office machines, storage of paints and chemicals, gas stoves, and parking garages. You can usually smell the contaminants from these sources. New buildings can be designed with separate ventilation for these areas. Advanced filtration — HEPA and electronic filters — can also improve air quality.

Why do it?

Garages and chemical workspaces are required to have separated ventilation; treating less intense pollutant sources similarly will improve health. Filters are important for sensitive individuals.

How to do this?

Plan your space layout and ventilation system with future uses in mind. Place filters in locations where they can easily be changed and maintained.

Who does this?

Architects, mechanical engineers.


area one

Use clean and efficient alternatives to wood–burning fireplaces

What is this?

Wood–burning fireplaces have very low temperature fires, creating lots of pollutants in their smoke, which cause a significant health hazard both indoors and outdoors.

Why do it?

A number of jurisdictions in San Mateo County have already prohibited the installation of new wood burning fireplaces as a result of this hazard. Additionally, fireplaces are inefficient heating sources, providing relatively little heat and causing cold drafts, and wasting heating fuel, unlike alternatives.

How to do this?

Alternatives to wood–burning fireplaces include wood stoves and gas fireplaces.

Who does this?

Building owners, architects.


More Information

Radiant Panel Association
Bay Area Air Quality Management District
Green Resource Center