Who among us has not felt a draft pass through their house on a windy day or been at a friend’s noticeably uncomfortable condo? Why is one room in your house much warmer than another? How do I make my home comfortable and keep reducing my energy bills? How do you even define “comfort”?
It’s important to understand some building science when you are working toward improving your home’s energy efficiency which in turn will reduce your monthly energy bills. Houses are very complicated and have many systems installed to defend its occupants from the elements, while also maintaining a relative comfort level.
If your house is uncomfortable and you are interested in correcting that, while also potentially reducing your energy bills, read on!
The Deep Dive On How To Reduce My Energy Bills
Allow me for a moment to really “nerd out” I’m not going to tell you that in order to save energy in your house, all you need to do is install some new light bulbs. To really get to the heart of the matter it’s important to understand the forces that your house is working against.
“Cold” is relative. What is cold to a person is only a small sliver of actual cosmic temperature differentials. Humans are fickle and needy. We can really only tolerate temperatures in a very small window.
If anyone of us were to suddenly find ourselves standing on either the sun or the moon, you would know exactly what I mean! “It’s cold today!” A common exasperation, but in the most clinical terms, inaccurate. However, it would be pretty weird to hear someone say “Boy, it sure is less warm today!” even if that is more accurate.
So how does this concept apply to your house and how does it help reduce your energy bills? Let’s say that generally, a person wants to live in their house in the temperature range of 65 to 75 degrees and lives in a climate with a distinctly hot summer and cold winter.
The systems in your house will work to keep that comfortable and desirable temperature. Your furnace will burn natural gas, and an air handler will cycle that warm or “conditioned” air through its duct system throughout the house.
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Similarly, in the summertime, your air conditioner will extract heat from your house and pump it outside. Ah, you say! But doesn’t an air conditioner create cooler air and push that through the ducts? That is true, but only as a by-product of the system’s purpose, which is to remove heat.
In order to wrap your mind around energy efficiency, you must understand that energy always moves from high pressure (warm) to low pressure (less warm). Your house is waging a war against the sun. That’s a tough fight and one that can easily be won by the sun.
In the summer, the sun heats up your house and everything around it. Your poor little air conditioner runs its heart out to pull that heat out of your house, while the heat is unrelenting in its pressure on your house.
In the winter, your furnace runs to fill your house with warm air, which will inevitably bleed through even the best walls to return to an area of lower (less warm) pressure.
So what can we do to reduce the consumption of fuel in this endless fight with the sun?
Houses have features that limit the amount of undesirable energy transfer.
A perfectly energy efficient house has never been built and will never be built. Energy will transfer through the house and be lost. Super high-efficiency houses can only “offset” the energy loss, usually done through the installation of photovoltaic solar systems.
So, the very best energy efficient houses have systems to limit undesirable energy transfer. Houses use fuel to produce heat energy or remove heat energy. A more traditional house will use natural gas to fuel its furnace and its water heater.
How effectively that furnace or water heater is able to turn that fuel into energy is outlined in the units “AFUE” Annual Fuel Utilization Efficiency.
The more typical furnace of the ’80s and ’90s could achieve an AFUE of 80%. Better, but still room for improvement.
The highest efficiency furnaces of today can achieve 96% AFUE or better, which is tremendous if you are interested solely in the energy efficiency of the unit. Interestingly, you may notice that the 100% AFUE furnace does not and cannot exist.
Similarly, your air conditioners will consume electricity to cycle their refrigerants to collect heat from the house and exhaust it outside.
So if you are interested in improving the energy efficiency of your house, that process can begin with upgrades to the heating and cooling systems in the house – an expensive proposition, but one that can pay long-term dividends.
Higher efficiency furnaces tend to pay for themselves over time by reducing the gas energy bills. The tradeoff is that you may need to live in the house for a long period of time before you see the full refund.
However, when a furnace or water heater is older and in need of replacement anyway, this can be a perfect time to opt for the high-efficiency units. The energy bill savings can quickly pay for the small difference in the premium price.
The walls and windows and how it relates to your energy bills
The much more practical application of building science to your house begins with Energy Retention. We are already consuming fuel to produce heat energy or remove heat energy, so why wouldn’t we seek out ways to reduce this overall energy transfer and keep the heat where we want it?
This is where the conversations about R values and insulation kick in. Your house is encased in a thermal boundary, a building envelope, or for people who aren’t big nerds, it is basically the walls and ceilings that provide this boundary.
For some reason, no one wants to live in a dome with no doors or windows, even if that is the most energy-efficient design. There is a very good reason that an Inuit igloo is shaped like a dome and it is not just for simplicity of construction.
Energy can and will pass through your walls and windows. So the fight for energy retention becomes one of limiting the transfer of energy through the thermal boundary. So, it’s not a crazy idea to consider ensuring that your walls are well insulated.
Even a modest 2×4 wall can achieve R-13 insulation levels when properly installed. But gravity, much like the solar energy from the sun, is a harsh mistress and will slowly weigh down insulation in the walls and create uninstalled gaps along the tops of the walls.
It’s worth noting that windows are an inherent vulnerability. Even the best triple pane low E gas super windows cannot achieve the insulating value of a very typical wall assembly. But again, no one really wants to go that far and get rid of their windows.
There is a point of diminishing returns on windows, where you will spend a huge amount of money for very little gains in energy efficiency. Generally speaking, if your house has a double pane vinyl window, you’re okay.
In this case, replacing the windows should be first on the list. Although windows will never be perfect, this is one of the best ways to increase the comfort levels of your home.
Heat rises, so push it back down.
Insulating an attic space can be a very cost-effective way to limit energy transfer. If you don’t have a lot of attic insulation having a company blow in more can be one of the cheapest insulation upgrades.
If you are on an even tighter budget, you can watch some YouTube videos about how to install insulation and do it yourself, so long as you know how to safely get around in an attic space.
There are a few products in wide use today, each with their pros and cons like anything else. But an attic space insulated to R-49 (15 inches) can really make a difference in your energy bills!
One thing to watch out for and which very often gets overlooked is the ventilation of the attic space. Your attic space needs to breathe. Homes can be equipped with vents at the eaves to allow air into the attic and vents at the top to exhaust heat. Air exchange in an attic space can play a large part in the overall energy efficiency of your house.
If your attic cannot vent out heat and exchange air then it will hold on to that heat, and moisture concerns could occur. Imagine that you are asking your air conditioner to remove heat from the house but you have a huge hot blanket over all of the rooms.
It will only make your air conditioner work that much harder!
Your house may have some particular problems to overcome that make ventilation difficult, but there are products for that, too, such as a solar-powered thermostatic attic fan. These units can be installed to turn the sun into an ally and mechanically vent an overheating attic space.
Venting and insulating your attic property can amount to a huge energy bill reduction in the winter and summer!
But what about the draft!
So why is your house drafty? Why is your friend’s condo uncomfortable? I would ask you to think about these issues in the context of the building science principles behind these issues.
Maybe there’s a window that’s stuck open a little and you felt a draft. That’s a simple problem with a simple solution.
The best way to find air leaks in a home is by performing a blower door test and using a thermal camera to find air leaks.
This will give you a clear picture of what needs to be sealed and can even show hidden air leaks that would not be visible with the naked eye.
But what is the best place to start on your home to reduce your energy bills?
If you are interested in learning more about your house and its energy efficiency, I recommend that you get a full Energy Assessment by a qualified professional.
There is a lot of information out there about light bulbs, water fixtures, and photovoltaic solar systems, but I would encourage you to get a full assessment of all of your home’s systems and how these systems interact with each other.
Identifying the largest vulnerabilities in your house that can often be out of sight and out of mind can really make a positive impact on your energy bills and in your overall comfort in your house.