Heating and Cooling Your House
Your transition to all-electric living starts here.
How do you choose the best HVAC system for your home? How can you convert from fossil fuels to renewable sources of energy with the least amount of financial pain?
Make no mistake: Heating and cooling your home is the number-one source of energy use in most people’s lives. At the heart of many older systems is a furnace or a boiler, or in some warmer climates, an electric air handler.
Want more articles like this? Download the Homeowner’s Handbook of Green Building and Remodeling.
A furnace burns fossil fuel to heat air that’s forced by a blower fan through a series of ducts to the living spaces; a boiler heats water that’s then pumped to a hydronic, or water-based, distribution system.
Air handlers were common in the 1960s or so. They provide both heating and cooling, but prior to the introduction of heat pump technology, were quite inefficient.
Most heat pumps run on electricity. They don’t create heat, but rather extract it from the air or the ground. Heat pumps are available for use with forced-air and hydronic distribution systems. If you want to minimize your fuel bill, an ENERGY STAR rating is a minimum standard for these appliances.
Gas Furnace: Super Efficiency
If you must heat with gas, be sure the furnace is a newer, high-efficiency model (90% AFUE or higher). But using gas as a fuel source has outstayed its welcome. We’re only just learning about the many long-term negative impacts of “fracking” used in a lot of gas extraction.
And the climate change impacts are undeniable. No fossil fuel gets an environmental-free ride. It’s a finite resource, not a renewable one.
One way that newer technology squeezes more power from gas is with an exhaust heat exchanger. This exchanger steals back heat from the furnace’s waste byproducts. Another feature, flame modulation, adjusts the flame size, based on demand. Modern furnaces include variable-speed blower fans with high-efficiency electric motors.
High-Efficiency Boiler: Using Water to Warm Your Home
A boiler burns oil, natural gas, or propane to heat water. That water is then pumped through a system of pipes to radiators, baseboard heaters, or a radiant floor. A good boiler will offer efficiencies of 90 to 95 percent and will include many of the same technologies as a high-efficiency furnace.
These include a modulating burner that matches the heat output to whatever the thermostat is calling for at the moment, advanced heat exchangers to extract more heat from the same amount of fuel, and the ability to recover heat from the exhaust gas by condensing it. The resulting exhaust is cool enough to be vented out of a plastic pipe. In the best cases, this condensing process can squeeze 10 to 12 percent more usable energy out of the fuel.
Air-Source Heat Pump: Extracting and Moving Air
A heat pump is an air conditioner that works in reverse to provide warm air. The heat pump captures and concentrates heat from one area, then releases it to another.
To warm indoor air, the heat pump takes heat from the outdoor air and delivers it to the home’s distribution system. In cooling mode, it reverses direction to work like an air conditioner, extracting warm air from inside the house and blowing it outside. In cooling mode, this waste heat can also be used for water heating.
The most common type is the split system, which uses separate indoor and outdoor units, but you can also get packaged systems that place everything in a self-contained outdoor unit.
Air-source heat pumps can offer efficiencies of 200 to 300 percent but are most efficient when temperatures are neither extremely hot nor way below zero. Part of the “secret” to efficient use of heat pumps in a home is knowing how and when to adjust temperatures.
How much should you adjust your heat pump thermostat during sleeping hours? The general rule is no more than about 5 degrees. So if you normally keep the home at 70 degrees Fahrenheit, you could have the system drop down to 65 degrees at 10 p.m. and start warming up again to 70 at 6 a.m.
Although it doesn’t resemble any thermostat of the past, the Vivint Element Smart Thermostat probably represents the future of home heating/cooling control. As part of your smart home network, you can control it from anywhere with your phone, create schedules, automate changes and even receive alerts for various scenarios. Using a smart thermostat can save up to 30 percent on your annual energy costs.
Geothermal Heat Pumps: Putting Soil’s Stability to Work
Also known as ground source heating, this time-tested technology has seen a recent surge of interest. In a typical application, a pump forces refrigerant through underground piping loops, installed horizontally or vertically, to exchange heat with the earth. This is much less energy intensive than an air-source heat pump, which may have to extract heat from cold winter air.
Once this pre-heated or pre-cooled liquid reaches the house, most of the “work” is done, and the exchanger can then extract this free energy for use in the home.
The barrier to widespread use has historically been the higher cost of drilling and installing the pipes. But as fossil fuel prices increase, and solar power becomes ubiquitous, ground-source heat pumps offer an efficiency advantage over air-source HVAC. Because 70% of their heating capacity comes from the natural warmth of the ground, a relatively small solar-plus-storage-plus-geothermal system can heat your home.
How much money can you save over time by heating or cooling with geothermal? Here’s an interactive calculator from WaterFurnace to help you make the calculation.
Domestic Water Heating: Get Efficient!
In most homes, a separate tank heats the hot water that you use to take showers, wash dishes, and so on. Traditionally, these tanks have used natural gas, propane, or electricity as their energy source.
Now, however, the market is gradually switching over to either tankless “on-demand” water heaters (most still rely on gas), or hybrid heat pump models that extract heat from the surrounding air. We recommend transitioning to one of these electric hybrid systems because it can be powered by renewable energy. Along with creating hot water, they remove humidity from indoor air and typically save more than 50 percent of what you would spend for a similarly sized conventional gas or electric hot water tank.
Boasting water heating efficiency of three to four times better than similar sized conventional tanks, the Rheem ProTerra Hybrid Heat Pump Hot Water Heater comes in 40-, 50-, 65,- 80-gallon capacities. Easy to install, it comes standard with onboard wifi compatablity, an integral leak detector. Control it manually with your phone, or set it to Energy Saver mode, for the most efficient heating strategy. www.rheem.com
Mini-Split Heat Pumps
Ductless mini-split heat pumps, or MSHPs, have improved dramatically over the last five years. Ductless systems are quieter, more efficient, more affordable, and capable of operating at greater extremes of temperature than their earlier incarnations.
A mini-split system consists of two main components: an outdoor compressor/condenser and an indoor air-handling unit. A conduit, which houses the power cable, refrigerant tubing, suction tubing and a condensate drain, links the outdoor and indoor units. MSHPs are quiet, efficient and flexible, and because there are no ducts, they are easy to install. Here are a few points to consider if you are in the market for a mini-split:
- Choose Variable Speed Models. MSHPs work best when allowed to modulate gradually based on demand. This also greatly reduces their noise and vibration.
- Know Yourself. Because MSHPs don’t rely on ducting to distribute air, they will tend to constantly cool or heat one room in your home. Ask yourself, “Is this the right location for a heat pump head?”
- Optimize flow. The number and output of MSHPs required to warm your home depends on its square footage, but also on your home’s layout. A small, very efficient open plan house might be served by just one MSHP, but in older homes with multiple doors and hallways, you may need several heads to achieve a good comfort level.
- Bigger May Be Better. Oversizing MSHPs—choosing units rated for a larger house—is okay. Oversizing can even be beneficial since MSHPs modulate their capacity and reach their highest efficiency when running at the lower end of their capacity range.
Mitsubishi’s 30,000 BTU Tri-Zone Mini Split Heat Pump includes three heads and one outdoor compressor.
Everything You Need to Know About Radiant Heat
Consider the four big benefits of radiant floor systems, and you’ll understand why it is specified in today’s high-performance homes.
Radiant floor heating—a concept that’s been around since ancient Roman times—isn’t a tough system to understand, install, operate or maintain. It’s one of those systems people hear about and think, “Wow. I’d like to have heated water circulating underneath my floor, warming everything it touches.”
Here are the four key benefits of in-floor radiant systems:
# 1: Comfort
“Comfort” is a key reason people consider installing a radiant heat system in their house. With radiant, warmth slowly rises from the floor as opposed to blowing down at different temperatures with a forced-air system. Radiant floor heating produces room temperatures at 75 °F at floor level, declining to 68 °F at eye level, and then to 61 °F at the ceiling.
According to the Radiant Panel Association, a radiant floor normally feels “neutral,” with a surface temperature lower than normal body temperature, although the overall sensation is one of comfort.
# 2: Efficiency
The water in a hydronic radiant floor system has 3,500 times the energy transport capacity of air, so it can heat (and even cool) using less energy than a forced-air system. This amounts to greater comfort at a lower thermostat setting, which provides reduced energy use and lower energy bills.
In fact, more people are comfortable with radiant floors set at a lower thermostat setting than with forced-air heating at a higher setting. In addition, a radiant heating system works in zones, allowing different areas of a home to be at varying temperatures.
# 3: Health
A radiant floor system provides very high indoor air quality because it does not use fans or blowers, which can circulate dirt, dust, and other allergens throughout a home. Plus, warm radiant floors can eliminate the need for carpeting, which is a breeding ground for dust mites, a very common cause of allergy-related respiratory diseases.
# 4: Cost
Before looking at cost, consider durability: A radiant system lasts two to three times longer than a typical furnace, primarily because it doesn’t have as many moving parts. The boiler system can last 20 to 30 years; the piping in the floor—radiant heat system manufacturer Uponor offers a durable crosslinked polyethylene (PEX)—will last for the life of the home.
The actual costs for installation and equipment vary greatly, depending on the manufacturer, type of system, the size of the area to be heated, type of zoning and controls required, flooring type, and labor cost. There are other factors as well, such as whether you are ripping out an existing floor or installing the system on a new concrete floor.
While radiant is more expensive up front than a forced-air system, by rolling it into your mortgage you can enjoy the benefits of the system immediately; if you choose forced air, you pay less upfront but will have higher utility bills, lower indoor air quality, and reduced comfort.
This versatile pre-insulated pipe system is ideal for radiant systems with underground distribution of hydronic heating, cooling and potable-water systems. Ecoflex features cross-linked polyethylene (PEX) or high-density polyethylene (HDPE) carrier pipe, surrounded by layers of PEX-foam insulation, all covered by a watertight HDPE jacket.
To learn how radiant systems work, visit Uponor.
Glossary of Terms
- AFUE: The Annual Fuel Utilization Efficiency is the percentage of a fuel’s potential energy that a furnace or boiler converts to usable heat.
- Air Handler: In a forced-air heating or cooling system, the air handler unit moves heated or cooled air through the home’s ductwork.
- British Thermal Unit (BTU): The unit of measurement for heat, whether it’s the heat given off by burning fuel or extracted from a home for cooling. Technically, one BTU is the energy required to raise one pound of water one degree Fahrenheit.
- Combustion Chamber: The part of a furnace or boiler where the fuel is burned.
- Compressor: The part of the air conditioner or heat pump that compresses and pumps refrigerant.
- Condenser Coil: The part of an air conditioner or heat pump that releases heat from the surrounding air in cooling mode and collects it in heating mode.
- Evaporator Coil: The part of an air conditioner or heat pump that exchanges heat with the air in the home.
- Heat Exchanger: Located in the furnace or boiler, it transfers heat from the combustion chamber to the air or water in the heat distribution system.
- Seasonal Energy Efficiency Ratio (SEER): The cooling efficiency of an air conditioner or heat pump. It’s the ratio of cooling output to electricity used. The minimum SEER requirement for units manufactured beginning in 2006 is 13.
- Zoning: A method of partitioning a home’s hydronic or forced-air distribution system into independently controlled comfort zones.
Publisher’s Note: This content is made possible by our Today’s Homeowner Campaign Sponsors: Whirlpool, Vivint, myQ, Sonos and Jinko Solar . These companies take sustainability seriously, in both their products and their operations. Learn more about building and buying homes that are more affordable and less resource intensive.