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nkenealy
HVAC or Windows First?
nkenealy

I own a circa 1940 house in Northern Virginia. I need to replace both the windows and the HVAC in the near future. Which should I replace first? Both are old - the windows are in bad repair and were basic when installed and the AC is over 25 years old but still runs. Thoughts?

dj1
Re: HVAC or Windows First?
dj1

Is this a central air unit or a wall/window unit?

keith3267
Re: HVAC or Windows First?
keith3267

Depends on how many windows. I am having some windows replace in a couple of weeks and they are $400 each. So if you are replacing 15 windows and your price is about the same, that's $6k, about the same as a new HVAC unit, not counting ductwork.

Lets say your annual heating/cooling bill is around $1000. If your heat loss through your windows is the typical 20% of the homes heating/cooling losses, then that accounts for about $200. Replacement windows should reduce the losses by half, and since windows make up the majority of infiltration losses which also account for about 20% of the total in a typical house, they should also cut those losses by half, or almost half anyway. So the replacement windows should save you almost $200/year for a 30 year payback.

I'm just guessing that your 25 year old HVAC system is about 70% efficient. I think that is typical of that era. A low end new system should be at least 80% efficient and more expensive systems can get over 90% efficient. You are looking at a $100 to 200/year savings here too, or a 30 to 60 year payback.

Plug in your actual numbers here, quotes for the windows and HVAC, efficiencies and your actual annual heating/cooling costs and use the same logic to determine which gets you the most bang for the buck.

And don't forget, comfort has value too.

Fencepost
Re: HVAC or Windows First?
Fencepost

If the ducts in unheated areas (crawlspaces, basements, attics) are not properly sealed, sealing them up so they don't leak air will make a huge impact on the efficiency of the HVAC unit. You may be able to seal the ducts yourself for less than $100 in materials.

Jack
Re: HVAC or Windows First?
Jack

A properly maintained HVAC system has a life expectancy of between 15 and 25 years. So your decision will need to include your willingness to gamble on a system that old and will you be able to replace if it fails after paying for windows. Second, windows generally do not need to be replaced all at once so they can be replaced over time.

Jack

A. Spruce
Re: HVAC or Windows First?
A. Spruce

I would vote for HVAC over windows, yes, the windows may not be very efficient, but they do keep the weather out, short of someone throwing a brick through them. The same cannot be said for an HVAC system, which can let go without warning, leaving you without heat or cooling when you need it most. Now, heat is far more important that cooling, but still not something you want to gamble on. The likelihood of failure will be in direct proportion to level of demand upon it. If you never use it, it will probably last you another few years, if it is used heavily, then it is only a matter of time before it gives up.

You could pay for an HVAC inspection to get an opinion on the unit, but all that is really going to tell you is whether the unit is functioning properly in that moment, there will be no guarantee it will continue to function for any length of time after the inspection. One final thought, replacement of a unit is cheaper in the "off season" than when technicians are in high demand and can charge a premium for their time, particularly for emergency repairs/replacements.

nkenealy
Re: HVAC or Windows First?
nkenealy

Thanks for the thoughts. It's a central unit HVAC. Total house is about 20 Windows. If the HVAC died we'd be able to replace it. I'm mostly wondering about efficiency gains. Will we feel the difference with a new HVAC if the windows are still letting air in and out? Or will we care about bad Windows with a better HVAC? The duct work is reasonably insulated but it's very narrow. Seems smaller than modern ducts and seems like it was added after the original construction. Is $400 a window a good ballpark number for reasonable windows with instillation? We'd rather do all the windows at once. The price seemed to be higher for piecemeal replacement. Oh - and we would still be able to replace the HVAC if it died if we did Windows first. Again, just trying to prioritize expected expenses.

A. Spruce
Re: HVAC or Windows First?
A. Spruce
nkenealy wrote:

I'm mostly wondering about efficiency gains. Will we feel the difference with a new HVAC if the windows are still letting air in and out? Or will we care about bad Windows with a better HVAC?

You will likely feel an improvement regardless of which you do first. An efficient HVAC will not have to work as hard, even with bad windows, and it will have an easier time keeping up with the demand. Conversely, if the windows are improved, the aged HVAC won't have to work as hard either, so you're likely going to feel the difference here too. When you replace the HVAC, make sure that the ducting is checked too, not only for efficiency on its own, but that it is sized correctly for the house and the new HVAC system. An energy audit will help determine what you need and will take into account your windows, insulation, and HVAC system.

When it comes to windows, you need only ask how much you are willing to spend and you will find a window to fit that price line, that is to say, you can pay as little as one hundred and as much as several thousand dollars per window, depending on size, number of panes, gas fill, frame type, coatings, etc.

Jack
Re: HVAC or Windows First?
Jack

As far as costs, I believe this site has an estimater.http://windowsremodelconnection.com/3step?SRC=Aff708&Pub_ID=61416956375&Sub_ID=105482

Jack

dj1
Re: HVAC or Windows First?
dj1

" It's a central unit HVAC."

That was what I thought, and in that case, go for a new A/C unit. Get as many estimates as you can, and do it right away. Summer time is the wrong time to ask for estimates or to sign a contract.

A reliable A/C tech will be able to suggest the right equipment for you - how many tons and SEER. He will look at your ducts, return and register locations.

keith3267
Re: HVAC or Windows First?
keith3267

There is one possible advantage to doing the windows first, it may mean that you can downsize the HVAC. Again, this will take some analysis but if the next size smaller would "almost" do the job, new windows could make the difference.

Getting all the windows at once has the advantage that they will all match. Doing them over time risks the window maker going out of business or a model you like going out of production. $400 windows that I am getting are wood/composite dual pane mid grade windows from a small manufacturer. Windows can run from $200 to over $1000 each depending on the features you want. You need to find a local remodeler and get quotes.

Check with local building material suppliers for recommendations. Do not go to big box stores for recommendations as they are far less likely to really know the contractors they deal with.

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