Heating and cooling supply vents are almost never installed right which is costing you money. First, the vent should be sealed off during construction to prevent debris from falling into the opening, but also for job site safety. This will prevent blockages in the duct from various debris to block air flow.
The vent should also be tied tight to the subfloor using mastic. This reduces the amount of air that will hit the bottom of the register and flow back down into the room above or below. This allows the air flow to work closer as was designed.
Green Term Defined: HVAC (Heating, Ventilation, and Air Conditioning Mechanical System)
HVAC stands for the Heating, Ventilation, and Air Conditioning system in your home or business. The system should be able to heat and cool your home to create a comfortable living environment. It should also have a source for bringing in fresh air and to control humidity. An HVAC system is designed by a mechanical engineer based on the principles of thermodynamics, fluid mechanics, and heat transfer.
An effective HVAC system will keep the fresh air in your home comfortable and healthy. A proper ventilation system has air filtration that removes toxins from the indoor environment. A properly designed HVAC system should include a ventilation strategy as well as heating and cooling capacity. Ventilation includes both the exchange of air to the outside and the circulation of air inside the thermal envelope.
Your heating and cooling system should be inside your thermal envelope or you are wasting money. We often find the HVAC system in homes in unconditioned attic, basement, or crawl spaces. That means you are trying to cool or heat air and send it through a space that is working against that goal. You are also probably growing mold.
This not only means the HVAC mechanical equipment should be on the conditioned side of the insulation, it means the duct work should as well. While duct work has insulation, it is not as much insulation as you should have between inside and outside of your home. Keeping the mechanical system and duct work on the inside of the insulation will reduce the amount of energy required to achieve comfort.
If you mechanical system is in an unconditioned space, you are wasting money. The best solution is to add insulation to the space placing the mechanical system inside the thermal envelope. It is not a simple problem to fix if it was not done with building science in mind to start. However, it is a problem that should be solved for lower energy bills and higher comfort.
In the average new home with a forced air heating and cooling system, 30% of the air moving through the ducts leaks out before it reaches the room it is intended to heat or cool. Seal up the ducts for a better distribution of air throughout your home using mastic tape or glue. A properly designed, calibrated, and maintained system will run more efficiently. Remember to change the air filter on a regular basis to keep the air flow as designed. You may also need to have your ducts cleaned to increase efficiency of your system.
Windows are often blamed for the uncomfortable conditions of an older home, but there are bigger holes in almost all cases. Remember to look for these places that heated air is escaping from your home including the attic access / pull down stair, recessed lights, electrical outlets, and rim board. Seal these locations and reduce your energy loss.
When winter comes a warm fire is often not far behind for those fortunate to have a fireplace. However, when the fireplace is not being used, make sure it is sealed tight. At the very least, close the flue when not burning a fire. You might also consider adding air tight doors if you don’t already have them or using a fireplace balloon to make it air tight (just remember to remove the balloon before using the fireplace.
Make sure your outside mechanical equipment is cleared of any debris, snow, or landscaping that might impact the operation. Most units need 24-36″ of air space in order to run efficiently.
Almost always overlooked when talking about electrical usage is water usage. Heating water is taking a toll on your monthly electric bills if you have an older water heater, uninsulated hot water supply pipes, and water inefficient fixtures. Turn the tide on this impact by installing a heat pump hot water heater, insulating pipes, and changing out fixtures to WaterSense labeled options.
Efficiency: You wouldn’t purchase a jet airplane to get to the other side of town, right? It would not address the need directly and it would cost a fortune to run and maintain. The same is true for your heating, cooling, and ventilation system.If your system is oversized as many are in residential projects, it means that you are paying more than you need to maintain the air temperatures in your home. Your goal should be to get a system that is right sized. If the right sized system runs for an extended period of time, it will filter air and control humidity, while maintaining the comfort levels in your home. This right sized system will cost less to install and to operate.
Comfort: No matter what you have heard, bigger is not better when it comes to HVAC systems. An over-sized air conditioners will not dehumidify the air inside your home. The typical air conditioning units need 10 minutes of running before the coils get cold enough to cause condensation. This the needed to dehumidify the air in your home. If the system is oversized, the thermostat will be satisfied in under 10 minutes (short cycling) well before the unit is able to remove a significant amount of moisture from the air. This creates a cold, clammy condition that is not comfortable. A right sized air conditioner should produce relative humidity levels of less than 50% in the cooling season inside your home. This will improve your indoor air quality and feel more comfortable. Heating season comfort is also impacted by over-sized heat pumps. They produce supply air that is roughly 100 degrees, compared to furnaces that produce supply air that is 125-135 degrees. The result is a heat pump having to move more air around the house to deliver the needed amount of heated air. If a heat pump is oversized, more air than is necessary will be moving around the house, creating drafts, and causing complaints about comfort or causing you to turn up the thermostat. Heat pumps should be right sized based on the insulation, orientation, air leakage, windows, and size of the home.
Air quality: If your system is over-sized and therefore not properly dehumidifying, you’ll most likely have moisture problems. This could result in strange smells, mold or mildew growing in areas that don’t receive much air flow, excessive presence of dust mites, etc. Air quality will be impacted unless the system is right sized.
Your heating (ventilation) and cooling system uses more energy than anything else in your home. There are many things that could hamper the effectiveness of the system costing you money and comfort every day. Finding places that are causing problems and costing you resources is the first step in getting your home’s systems right, cutting your energy usage, and increasing comfort around the home.
One place you might not think to look to fix interior comfort is on the exterior. The exterior unit must have proper air flow around the entire unit. Cut back overgrown vegetation to give the proper clearance to the units. This allows the unit to function as designed.
The ducts inside your home (attic, basement, and crawlspace) should be sealed with mastic, NOT duct tape.
Ducts in the crawl space should have proper insulation around them to prevent sweating.
The average forced air duct system leaks 30% of the heated / cooled air out of the duct before it reaches the room it was intended to heat or cool. A very good installation only leaks 10% of your money out of the ducts typically into an unconditioned space.
While mastic can do a lot to reduce air leakage from the ducts, keeping the ducts into the conditioned space reduces the money lost.
Getting your HVAC system efficient is a great way to reduce your wasted energy each month and will make your home more comfortable on a daily basis.
I say it all the time, your home is the most complicated machine you own. One of the main reasons for this statement is your (HVAC) Heating, Ventilation, and Air Conditioning Systems. If you have a forced air Heat Pump that is controlling the temperature in your home, you are like most in our area. This is the least expensive option for a system and most often used solution for heating and cooling. Notice I left out the V (ventilation). This is one place where the problems start. If you build a tightly sealed efficient home you need to have a HVAC system that is bringing in fresh air for air quality, dehumidification, and for health. Another place where the wheels fall off of a traditional ducted HVAC system is the supply registers in your rooms. If they are installed properly, you will not see the edges of the metal duct when you take off the register cover as you see in this picture.
If done properly a duct boot has mastic on it at the sub-floor creating a tight air seal so you will see directly into the duct and will not have air space around the edges.
This proper duct sealing also shows up on the ducts themselves – which you can see here.
These simple steps done during construction could cut your energy use for Heating, Ventilation, and Cooling by 30% monthly. Now that really could add up quick!
Yesterday I read another great blog post by Energy Vanguard (if you don’t know these guys you should). This post focused on the Today Show’s ‘sting to see if HVAC contractors would do the right thing when brought to a home to diagnose a heating and cooling problem. As you might expect, the results were ‘made for TV’ and nobody that made the cut to be shown in the episode did an honest job, some even proving to be outright crooks. So moving past the sensationalism aspect of this television investigation I want to look at the issues that really exist in the industry as a whole.
When a HVAC contractor is called out to a home to address an issue with the “system not cooling like it should” it could be a variety of factors.
The homeowner does not understand how to program the thermostat
The system is not working correctly
The system is not sized correctly (this is actually probably the most common issue)
The system is not distributing air correctly (ducts not designed right, someone crushed a run, dirty ducts)
The refrigerant level is low
It is the hottest day on record and the system cannot keep up since the system is in the attic that is not conditioned
I am sure there are more issues that I did not think of for my list. The other problem is the level of training the service tech that shows up at your front door might have gotten prior to getting to your front door. If you simply picked up the phone book and found the company that offered a free review, or fast service, or has the first listing, you have no idea of their track record, ability to actually fix the issue, or ability to understand the problem. A HVAC system is not a simple appliance like a stove. It is a complicated piece of engineering that has many factors, parts, and influences. This may be the most complicated part of your home to manage, understand, design, and diagnose. The HVAC tech that comes to your home to figure out how to address your problem with the system needs to understand how the mechanics of the system function, how the mechanics of the home impact the system, and how the environmental conditions may impact each of those elements. If they are working on a fixed fee and get bonuses for up-selling, the temptation may be too great not to resist giving you some questionable information about your system. However, if you hire a reputable contractor that has the appropriate training (ask them about building science, BPI certification, insurance and license, and past clients that you can call and talk to) you should not have to worry about getting sold something you do not need.
A home is complicated. Designing and building a home is more than just understanding carpentry, it should also be understanding building science, carpentry, spacial flow, functionality, design, aesthetics, proportions, zoning, usability, indoor air quality, material science, and much more. The construction industry as a whole is running towards a new standard of what is acceptable, but we are not there yet. Almost every seminar I go to now shows a slide of air leakage in homes as this is the low hanging easy thing to fix to show clients added value. The problem is once you make the house tight, you open up another layer of the onion with humidity issues, water infiltration, and air quality. The education is coming, some have jumped on board early and “get it” and some are still trying to figure out how to change their standards (the construction industry is VERY slow to change). Reports like this one done by the Today Show are only an added value to the discussion if they also show the guys doing the work right and tell you how to find a qualified solution. Running a sting is about ratings, providing solutions is about quality.