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New HVAC system vs insulation?

Hopefully I have posted this on the right thread - if not I apologize. My wife and I are trying to decide on whether we would be best to upgrade our HVAC system or add insulation to our house. I know that this shouldn't really be an either or, but both cost $$ and we can only do one. To help with any suggestions, here are some additional details:

Our house is a 1948 brick ranch house in central Alabama. The walls have no insulation and the attic has some older insulation (estimated R-value of about 10). The roof is a light colored metal. Our HVAC system includes aging ductwork and a massive air handler/furnace unit that is probably 30+ years old. The AC unit is around 6-8 years old. In the summer our AC unit will run for about 12 hours a day (continuously). In winter the furnace never runs for more than about 30 minutes.

We have received quotes for a new heat pump/air handler package with new duct work and would love to go with that option, but at this time it would be a strain on our limited resources. The other option that we are considering is adding insulation to the attic and possibly adding sprayfoam insulation to the exterior walls. Based on the estimates we have so far, the insulation would cost about about 1/8th of the cost of the HVAC system.

The question that we are trying to answer is: which would be the better use of our limited funds - a new HVAC (heatpump) system (including ducting) or adding additional insulation?

Re: New HVAC system vs insulation?

If it was my house I’d go with the insulation.

Think of it this way. More efficient heating and cooling equipment will provide the same heating and cooling but will use less energy. Your heating and cooling load on the house will remain the same but your energy costs will be reduced. You can get a rough estimate of how much less your energy costs will be by comparing the efficiencies of your current systems with the new system. Say your current system is 70% efficient and the new system is 90% efficient. Your energy costs with the new, more efficient system would be 70/90 = 78% of your current energy costs. (Keep in mind this is a rough estimate.)

If you insulate the house you will reduce you heating and cooling load and that will save you money and make your house more comfortable (eliminating drafts, cold spots, hot spots, etc.) You have a lot of wall surface and ceiling surface through which you are losing or gaining heat. Increasing the R value of your insulation will reduce that rate. If you double your R value you cut the rate of heat loss/gain in half. Since you have no insulation in the walls you will be able to greatly increase your R value by adding insulation to the walls. And you can beef up your insulation in the attic. Insulation is a one-time expense that keeps on paying you back.

Later on you can use some of the money you save to buy more efficient heating and cooling equipment.

Re: New HVAC system vs insulation?

I agree with Sherry. If you update your insulation, especially with foam, you should cut the operating time down on the existing system and save enough money to update the system later.

Re: New HVAC system vs insulation?

Just some additional thoughts: I would agree that insulation will enhance the operation of any system, new or old. Some things to keep in mind are:

The air conditioning and heating system (if properly sized when installed) will be oversized with the improvement in "r" value the insulation adds. (I would venture to say if the system is very old, "rules of thumb" were used and not heat loss / heat gain calculations). Belive it or not, there was a time, not too long ago, where the bigger is better attitude prevailed in our industry. That is NOT the case today. For proper operation, the equipment has to be matched to the load and therefore matched to your home's characteristics.

If the existing system doesn't have to cycle as often to maintain a comfortable temperature, great. But, if the change in "r" value causes the system to 'short-cycle' this can actually increase your operating costs. It requires much more electric to 'bring on' the appliance rather than have it up and running during that same time period.

I am somewhat surprised that your a/c has to run virtually non-stop to keep the home cool, but the furnace cycles off after twenty minutes?

I would certainly make the investment, before your larger investment of having the HVAC system thoroughly checked out by a qualified contractor, and let them give you their honest evaluation of the system. The only thing worse than having to decide whether to do the HVAC or insulation, would be deciding on the insulation and then discovering a problem with the HVAC system that has to be dealt with.

With where you live, I would strongly suggest a dual-fuel system if and when you do upgrade. This is a combination of heat pump and fossil fuel, providing you with the best efficiency from each fuel source (electric and gas) when each performs best.

All the best, Irishmist

Re: New HVAC system vs insulation?

Thanks for the great suggestions and explanations. We have had the AC system checked and it is working correctly. A couple of details that I probably should have included in the original post:

The furnace is massive - when it kicks on in winter the air from the vents is very warm, which probably explains the short run time. The other part is that it also kicks on quite often. One of the HVAC guys who gave us a quote estimated that the furnace was about 130,000 BTU and far to big for our house.

The AC is probably hindered by the air handler, which is not that great. The air handler is pretty old (30+ years) and has a number of leaks which affect both the air quality and the efficiency of the unit.

We will probably add insulation in the next couple of months (sooner rather than later) and then go from there with the AC system. When we do replace the system we will probably go with the dual fuel system and a decent filter system.

Thank you to all of you for all your helpful suggestions!

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