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HVAC 101: Small home upgrades that save big.

HVAC energy tips from Nest

This is the first in our HVAC 101 series, where we look at how your heating and cooling system works, and how it could work better.

In many homes, the heater seems to be on forever before you get warm. Or the AC’s humming, but you don’t feel any cold air. So you think something big must be wrong: the heating and cooling system is broken or all the windows need replacing.

But before you start a major energy upgrade with major costs, do something simple: look up, look down. The typical home has holes that leak out a full third of its heating and cooling costs.

The biggest issues happen where you can’t see them.

Often the first things we focus on when thinking about energy efficiency are windows and the cracks around them. But those tiny cracks are, well, tiny.

The really big holes, the ones you can put a fist through, are in the places you don’t go—in attics, basements and crawlspaces. That’s where wires, plumbing or heating ducts enter and leave the house or where foundation meets frame.

Not sure if you have a leak? Go to your attic and look for dirty insulation. The dirty spots show where air is traveling through the insulation and out of your house. Then go to your basement and look for gaps between the concrete foundation and the wood frame of the house.

If you do find leaks, you can contact a contractor to fill them for you, or you can often fix them yourself if you’re feeling handy. Here’s how:

In the attic:

  • Pull back the dirty insulation and find the hole. If the gap is under ¼ inch, use caulk. For larger gaps, use expanding foam or weather stripping. Then put the insulation back in place.
  • Locate openings around plumbing vent pipes and electrical wires. Seal them and cover with insulation.
  • Keep in mind, you may need more insulation. You can figure that out quickly by looking at your uncovered attic floor. You'll need more insulation if the rafters are visible.
  • Complete the job by sealing your attic door with weather stripping so it seals when closed.

In the basement:

  • Seal any gaps where the basement ceiling meets the frame of the house.
  • Seal areas that go through the basement ceiling to the floor above. These are generally holes for wires, water supply, drain pipes and heating ducts.

Before you change your system, seal your ducts.

Some homes may be perfectly insulated with no air escaping outside, but they’re betrayed by bad ductwork.

If the ducts that carry warm or cool air throughout your home are leaky, you could be losing 20% or more of that air before it even reaches your room. And the holes in ducts—just like the holes in insulation—are usually where you can’t see them: the attic, crawl space and garage.

Most homeowners choose to work with a professional contractor for duct improvement projects. But if you want to take on duct sealing as a do-it-yourself project, here are a couple steps you can take to seal your duct work:

  • Find any ducts you can access in your home’s attic, crawl space, basement or garage.
  • Seal any air leaks you find using mastic sealant or metal tape. Although it seems like duct tape fixes everything, don’t use it here. It won’t last long and doesn’t react well to heat.
  • Check and seal any gaps in the connectors where the ducts meets floor, ceiling and wall vents.
  • Wrap any accessible ducts in insulation.

Not sure where to start? Get an energy audit from a Nest Pro.

If you’re not sure where leaks are or how to fix them, an energy audit from a Nest Pro will help give you a complete picture of where your home is losing energy. It could also lead to 5-30% savings on your energy bill. Check to see if your utility offers incentives for audits or for insulation or air and duct sealing.

Have other energy saving tips or questions? Join the conversation in the Nest Community.