May 20, 2022
Are you looking to install a new heating and cooling system? In this short article we’ll try to help you make sense of heating and cooling technologies, considerations and terms so you are ready to make an educated call for your project.
Here are the questions you should ask yourself before deciding what system you should go for:
Are you planning to go solar?
Does the structure have the space for the ductwork to go through?Do you care about energy efficiency?
Are you more sensitive to the installation cost or to the operation cost?Do you care about the environment? Is the property in a subfreeze climate? Do you need both heating and cooling?
Would you want to heat or cool different parts of the house separately?
Are you comfortable with air flowing in your living space in the winter?
Can you handle condensation water draining?
Are you adding square footage to the house?
Do you need effective air filtration?
Are you looking to control the climate specifically in one room or an area of the house?
Are you sensitive to noise?
At what level your house is insulated?
Heating Technologies- There are 3 major technologies used residentially for heating: Resistive heating, heat redistribution and combustion. As fuel cost and global warming become top of mind for many people, more and more people are moving away from combustion heating which basically means you burn some type of fuel, be it natural gas, propane, oil or wood. Burning fuel always involves some level of energy inefficiency and air pollution, using electrical appliances for heating will result in higher efficiency, be it resistive at the lower end or heat pumps and mini split at the top energy efficiency.
Cooling Technologies - Broadly all residential cooling appliances are using the same technology- Refrigeration Cycle. Refrigeration cycle is a technology used to redistribute heat between two places. Simply put, it takes the heat from your indoor space and redistributes it outdoors. That’s why cooling systems typically blow hot air around their outdoor unit. Although there is only one main technology in use, there are an abundance of different appliances for residential cooling out there.
Resistive heating is used in electric radiators, electric furnaces, electric subfloor heating,baseboard heaters and more. These devices have electrical heating elements just like an electric oven and are considered cheap to purchase, install and maintain at the expense of low efficiency and thus high operating cost. If you plan to go solar, you should consider spending more money on a larger system which will compensate for the cost of resistive heating. After all, dollars spent on a larger solar system means more energy you generate year round that can be used for anything, not just heating.
Pros of resistive heating include: simple installation, tight temperature control(when combined with the proper thermostat) and it allows independent temperature control per appliance installed. It also takes a minimal amount of space, and can be retrofitted in existing living spaces. These devices are also silent and very comfortable to use as there is no air flow or minimal air flow. The purchase price is low, it requires no ductwork or copper tubing, involves no emission, assuming the electrical power is generated cleanly, which is most likely the case everywhere in California.
Cons of resistive heating include: low energy efficiency, the fact that it's a heating only solution, It uses electrical power which may mean expensive operation cost if used extensively and not paired with a solar system.
This technology is used in all the modern appliances and allows heating and cooling in one system. Mini splits and heat pumps are using heat redistribution, they simply move heat from the cool outdoors into your warm house, they use the electrical power to make refrigeration gas and air flow and not to generate heat. Their efficiency factor is higher than 1 and can go up to 3. This type of hesters (and coolers) exchange heat with the air outside, and in extreme weather places with the ground (geothermal) or with a water source. These appliances have three main parts, evaporator(or coil)- which is the part that distributes the heat inside your house, condenser which is the part sitting outside the house and exchanges energy, soil or water and the compressor which sits with the condenser.
The evaporator may warm up water(that’s why heat pumps are used to heat swimming pools) or air. In case that it is used to heat air, the living spaces would typically be heated through air ducts(forced air), or the evaporator can reside within the living space, like in wall mounted units or ceiling cassettes. In case the evaporator warms up water, the heat can be transferred to the radiators, sub-floor heating coils or other indoor units.
Air ducts or Ductless
Another main feature that varies across different types of systems is the co-location or split between the condenser and evaporator. A window unit combines the two in one box, making installation cheaper while compromising on the aesthetic and noise. A mini split, as its name suggests, has the condenser and evaporator split between different locations, allowing lower noise levels, different sizes of systems and multiple indoor units operated by a single outdoor unit. Air Ducts allow for one central appliance to take care of heating and cooling of the entire residence, while air ducts distribute the air to the different rooms.
From an energy efficiency and convenience perspective, ductless systems are superior to air ducts systems, the reason is the energy loss involved with hot air (or cold air) traveling in the ductwork. Ductwork are typically insulated and air tight but they are installed in the attic or in the crawl space which aren’t insulated. Over the years, their insulation degrades and air leaks from the joints causing significant energy loss.
This category includes gas and wood fireplaces, furnaces fueled by natural gas or propane and many other less popular heaters involving natural gas, propane, wood, oil and or other fuel types. Some of these heaters reside in the living space and are part of the interior design, some are installed in the attic or in the garage, and the hot air is distributed through an air ducts system. Energy efficiency of these appliances is the lowest, as some of the energy is lost with the smoke that’s being released and some energy is lost through the distribution process.
Yet,why is a natural gas furnace installed in most of the residential properties in California? Well, historically natural gas was a cheap source of energy and it was worth-while taking the hit of low efficiency while enjoying cheap energy cost.
Heating and Cooling Systems
With installation cost, energy cost, fuel availability and local climate, all being part of the equation, some combinations of different heating and cooling methods were developed as a sweet spot. That’s how most California homes ended up having a natural gas furnace and AC units which were built in originally, or were added later on. Some high elevation cold weather places were built with a fireplace, natural gas furnace and without any cooling.
What system is right for you
There’s no single answer, but here are a few things to consider.
Solar is mandatory for new construction in California, if you are building a new house you should consider sizing your solar system properly and installing a mini split or a heat pump so you minimize your utility bill and minimize your home’s carbon footprint. Mini split systems are also often the best solution for home additions, ADU’s, or any small living space. A unit for one room should cost $1200 to $2000 including installation which is most likely a lot less than upsizing your existing system and adding ductwork for your addition. People who work from home or spend a lot of time in a particular part of the property should also consider a mini split system with a wall mounted unit or a ceiling cassette which can control the climate in the particular space.
A furnace or other combustion style heating would be the right solution if you are in a place that loses power often, you can use a wall battery to operate the furnace because the gas would provide the actual energy used for heating.
A furnace is also the right solution in places that go to subfreezing temperatures for a long period of time. That's because a heat pump or a mini split outdoor unit may freeze and make it not effective or not functional at all in subfreeze climate, there is a way to overcome that by installing heating stripes on the outside unit, however it reduces it’s efficiency and if used very long may defeat the purpose of energy efficiency.
In the table below, we’ll provide an overview of Installation cost, maintenance cost, operation cost and environmental impact of different systems.
Heating and Cooling Glossary
HVAC- Heating, Ventilation and Air Conditioning. HVAC is a broad term used for all types of systems
Air conditioner- a system or process for controlling the temperature and sometimes the humidity and purity of the air in a house, etc
Split or Mini Split- refers to a refrigeration cycle system, where the condenser is installed outside and evaporator(s) is in or very close to the living space.
Ductwork- a system or network of air ducts, round or rectangular, 3” to 41” in diameter (or width) built in the attic or in the crawlspace, with the purpose of distributing air from (and to) a central appliance.
Ductless- refers usually to systems like a mini split or a VRF that does not use air ducts.
Ceiling Cassette- an indoor unit of a VRF or a mini-split that’s installed on the ceiling
Wall Mounted Unit- an indoor unit of a VRF or a mini-split that’s installed on the wall.
Efficiency- the ratio of the useful work performed by a machine or in a process to the total energy expended
Energy Star - energy efficiency program developed by the US Environmental Protection Agency. There are 70 categories and compliance sometimes makes a product eligible for rebates.
Zone- zone is typically an area of the house that can be controlled separately for convenience and energy efficiency.
Thermostat- a device that senses the inside temperature and controls the cooling and heating system. These devices can be very basic, programmable, or self learning according to usage patterns and other inputs.
Furnace- in heating and cooling furnace refers to an appliance that heats air centrally for the entire house. Typically run by gas, but not always.
Heat Pump- Unlike its name suggests, a heat pump can be used for heating and cooling. The name refers to the ability to transfer heat from one place to another.
Radiator- A device that distributes heat to the space around it. Used for heating, by hot water running through it or by electrical heating element.
Damper- a device that controls air flow used in air duct systems to control different zones.
Condensation- process where air humidity becomes water as the air runs through a cold surface. Condensation happens in the indoor unit while cooling and in the outdoor unit while heating. As part of a system installation, it’s required to drain the water properly.
Resistance heaters- any heating appliance that uses heating elements to generate heat.
Inverter- a technology that allows the compressor’s speed to vary, making the heating and cooling capacity a range rather than an on and off only.
Forced Air- refers to the part of an HVAC system that distributes both cool and warm air throughout the house, typically by air ducts
SEER- Seasonal energy efficiency ratio- basically cooling BTU’s produced annually divided by the Watt-hours that the appliance consumes annually. Numbers vary from 10 to just over 20, higher SEER means more saving in cooling cost (and higher purchase price)
HSPF- Heating seasonal performance factor. This term refers to VRF, Heat Pump or Mini split and talks about e
AFUE- Annual Fuel Efficiency Ratio. This term is used in fuel based appliances and boilers, and is the equivalent of HSPF in combustion based appliances.
BTU- British Thermal Unit, basically the amount of energy required to raise 1 pound of water by one degree Fahrenheit. It’s used to describe cooling(and heating) capacity because air-conditioners are just moving heat from one place to another.
Ton (or “Tonnage”)- the amount of heat required to melt one ton of ice in 24 hours(starting at 32F). 1 Ton = 12,000Btu, smaller units like Window AC units are ½ a ton and larger residential units are typically 3 to 7 ton.