Hello all. I have a house that is currently 1500 sq ft. It's brick and is on a dirt floor crawl space in humid SC. I'm sick of paying high power bills and have been investigating how to button up our home. It was built in 1968. All my windows are original. There is zero insulation under the house and the attic is poorly insulated. HVAC unit is 20 yrs old or older. So yeah I have some serious upgrading to do and aim to tackle it one piece at a time. Our AC is barely getting cold so next spring it will get replaced. That's a given. I'm going to try my best to seal up the attic. Attic I will remove all the old insulation, seal the soffits after installing attic baffles. Seal all seams and openings. Then blow in some cellouose insulation. I think that's a good start for air sealing the attic. After attic and HVAC are done I aim to replace all the old windows. After that encapsulate the crawl space. Am I on the right path to making my home more energy efficient? After or during all of this do I need to consider getting a energy air to air exchanger to get clean air in the house? Educate me and thanks in advance.

I'd get an energy audit and have them to calculate the ROI on each improvement.

Seal all seams and openings. Then blow in some cellouose insulation

Don't skip pressure testing while you can still do something about unexpected leaks.

I'd make encapsulating the crawl space a higher priority than windows, but you are on the right track. Here's two other websites that can help: building science.com & green building advisor.com.

Energy Star has a great guide to DIY air sealing. That can a be good starting point. Priority is leaks into the attic.

On air-sealing the attic floor you have to pay attention to all of the electrical, plumbing, and flue penetrations.

If you have ducts & airhandlers up there it would be better to bite the bullet and insulate & air seal at the roof deck, or rip it all out an install the HVAC in the crawl space. Duct boots are rarely well sealed to the ceiling gypsum, and any duct or air handler leakage creates pressure imbalances between the house and the attic (and by extension, the great outdoors), which drives air infiltration rates stratospheric while the system is running. This adds to the load totals, decreasing system efficiency and requiring bigger equipment.

Take Bob's advice- especially if there's room to run ducts in the crawl space, it will usually be much cheaper to insulate and air seal the crawl space walls & floor than it is to insulate at the roof deck, since the R-values and total surface area is much lower. Most tightened up 1500' homes with 2x4/R13 construction would have a cooling load of about 1.5 tons if the ducts are fully inside of conditioned space, but more than 2 tons with the ducts and air handler in the attic, above the insulation. If experience is any guide you probably have a 3-4 ton system right now, which is oversized enough to cut into comfort and efficiency. With a better 1.5-2 ton heat pump you could both heat and cool at high efficiency in an SC climate.

Jon's advice to calculate the ROI on each upgrade is a bit tough to follow, since there are many moving parts- the return of some upgrades will vary quite a bit by what you do about others. The more expensive HVAC & crawlspace solution may have a lousy ROI in the abstract compared to a high efficiency unit in the attic using existing ducts, but not if it means you can end up with a smaller unit and using half the power as if you'd kept it in the attic, and it's still probably cheaper than insulating to code min at the roof deck. There's a certain synergy that goes on and there are multiple moving parts.

When in doubt, putting the money into higher efficiency building envelope is better than putting it into higher efficiency HVAC equipment, and it sounds like there may be a lot of low hanging fruit on the building stuff.

If the windows are wood sash single panes in reasonable shape you'll get better bang/buck out of tightening them up and installing low-E storm windows than you would ripping them out and installing code-min replacement windows. If they're aluminum or steel framed windows replacement may be in order, but it's not as big a priority as air sealing and insulating the rest, or bringing the HVAC completely inside the thermal and pressure boundary of the house.

Thanks for the replies everyone. The attic is my first priority then the HVAC and then the crawlspace. Thankfully our ducts are already in the crawlspace.

Since the ducts are in the crawlspace, insulating and air-sealing the crawl space moves up the food chain. (That's triple-true if it's currently vented to the great outdoors.) You may be required to maintain a termite inspection perimeter strip on the interior of the foundation, but that strip can still be insulated with cut high density batt strips (rock wool preferred), easily removed & replaced for inspection purposes.

Running load calculations on the "after" picture of any insulation and air sealing upgrades needs to be done prior to replacing the HVAC, even if the HVAC is to installed before those upgrades are done. Odds are pretty good you'd peel at least a half-ton off the cooling load by reduced air infiltration, and more than that off the heat load by insulating the crawlspace walls. The improved attic-R will also add up to a good chunk.

If the duct layout is optimal you can probably do it all with a single 1.5 ton mini-duct cassette type mini-split, but if it needs more air handler than that (any longer runs?) there are better heat pump options.