TLDR: Help me sort my options on energy efficiency/cooling of my old(er) house.

Long-time reader of this forum but rarely post. I would love some advice/thoughts. We have a 1600 sq/ft early 1970's model house in College Station, built in a "modern" fashion, i.e. shed roof design. As typical of this era house it is extremely poor with regards to energy efficiency. Huge single pane windows that face the sun (lots of them), little insulation in the attic. Old ductwork in the attic that I am sure leaks. Probably tons of air leaks around the AC vents. It does have insulation in the exterior walls (which are mostly brick, but some wood exterior). The attic is hotter than blazes. There are technically two roof vents, but NO soffit vents or gable vents. Essentially no way to pull air to vent the heat.

With the above in mind, we are about to have to replace our two small A/C's. One of them was a home warranty Goodman (1.5 ton) that only cost me the $75 service call when it was put in (8 years ago) but it has given us trouble from the moment it was installed (very poorly) and I have been told by 3 different A/C companies that the best thing to do is replace the whole system. The other A/C is a 1989 workhorse (1 ton) that blows Artic ice out of the vents but has started leaking from multiple sites. Likewise, I have 3 different companies all telling me to replace. I agree with them.

My question is this. Before I replace the A/C's I am trying to decide if other energy efficient upgrades are worthwhile. I figure it is better to do any of this stuff prior to the A/C install as this might affect what size unit I get. I have been given several recommendations to go with at least 3 tons upon replacement. Obviously, I would get a Manual J before proceeding, but assume any insulation/changes I do might affect that calculation.
Help me decide what options I should do to improve efficiency. I don't mind spending some $$ but I not trying to be "net zero." Trying to pick best bang for my buck. Help me pick from the options below (and sort based from best to worst).

A.) Air seal the attic with closed cell spray foam closing off the roof vents
B.) Add soffits and gable vents to attic to vent the attic better
C.) Replace windows with double pane low-E
D.) Add tint to current windows to improve efficiency
E.) Replace all the duct work and A/C's with high SEER rating
F.) Do none of the above, replace the AC's with 13/14 SEER accept the higher monthly utility bills (which would be lower than currently since even basic units would be better than what I currently have).
G.) Other? Open to suggestions.

Thanks for the advice!

AEP Ag said:

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TLDR: Help me sort my options on energy efficiency/cooling of my old(er) house.

Long-time reader of this forum but rarely post. I would love some advice/thoughts. We have a 1600 sq/ft early 1970's model house in College Station, built in a "modern" fashion, i.e. shed roof design. As typical of this era house it is extremely poor with regards to energy efficiency. Huge single pane windows that face the sun (lots of them), little insulation in the attic. Old ductwork in the attic that I am sure leaks. Probably tons of air leaks around the AC vents. It does have insulation in the exterior walls (which are mostly brick, but some wood exterior). The attic is hotter than blazes. There are technically two roof vents, but NO soffit vents or gable vents. Essentially no way to pull air to vent the heat.

With the above in mind, we are about to have to replace our two small A/C's. One of them was a home warranty Goodman (1.5 ton) that only cost me the $75 service call when it was put in (8 years ago) but it has given us trouble from the moment it was installed (very poorly) and I have been told by 3 different A/C companies that the best thing to do is replace the whole system. The other A/C is a 1989 workhorse (1 ton) that blows Artic ice out of the vents but has started leaking from multiple sites. Likewise, I have 3 different companies all telling me to replace. I agree with them.

My question is this. Before I replace the A/C's I am trying to decide if other energy efficient upgrades are worthwhile. I figure it is better to do any of this stuff prior to the A/C install as this might affect what size unit I get. I have been given several recommendations to go with at least 3 tons upon replacement. Obviously, I would get a Manual J before proceeding, but assume any insulation/changes I do might affect that calculation.
Help me decide what options I should do to improve efficiency. I don't mind spending some $$ but I not trying to be "net zero." Trying to pick best bang for my buck. Help me pick from the options below (and sort based from best to worst).

A.) Air seal the attic with closed cell spray foam closing off the roof vents
B.) Add soffits and gable vents to attic to vent the attic better
C.) Replace windows with double pane low-E
D.) Add tint to current windows to improve efficiency
E.) Replace all the duct work and A/C's with high SEER rating
F.) Do none of the above, replace the AC's with 13/14 SEER accept the higher monthly utility bills (which would be lower than currently since even basic units would be better than what I currently have).
G.) Other? Open to suggestions.

Thanks for the advice!

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Go C, D, and E.

Replace the windows with double E and tint. Then replace the AC system and duct work (assuming it's not been changed in a reasonable time). Get at least a 16SEER unit to, but that depends on you're time you plan to live there (at least ~8-10 years longer).

Windows would be smart now, to help. But they'll be a lot more efficient. Don't change AC system until after the summer if you can avoid it.

We just changed our AC system last month (old one finally broke) and replaced the duct work. This month, we got our front (sun facing side) windows replaced with double low E. Expensive but it's much cooler and we'll see the returns in bills and appreciation when potential buyers look at our houses vs houses down the street who've not done it.

Just my two cents.

Thanks for the reply. I tend to think doing something to the windows would be a good choice as well. They're large and let in a ton of heat. Just can't decide if that's the right first move, or doing something about the attic.

Windows then Install radiant barrier foil in the attic if accessible. Do it yourself in the winter. I did mine and made a significant difference.

Agree with C,D, and E now.

Next time thr house needs painting add the sofits. While they've got everything cut open and exposed add blocking in thr joist spaces to keep your insulation off the sofits and keep that air pathway clear to the rafters.

If budget allows do a full hardi replacement and eliminate future rot after the repaint.

Windows first.

Is diy blow in insulation an option? If so, think about that in the fall.

Hadn't thought about radiant barrier. Will investigate this option more. Looks easy from a first pass.

Blowing in insulation is easy, have done it before. However was trying to decide if venting the attic some/any makes sense first. Or just fully enclosing attic via spray foam. I suspect there are air leaks all over the house into the attic.

Lots of recs for Windows. Will start investigating this more.

keep the ideas coming. Appreciate the thoughts.

AEP Ag said:

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A.) Air seal the attic with closed cell spray foam closing off the roof vents
B.) Add soffits and gable vents to attic to vent the attic better
C.) Replace windows with double pane low-E
D.) Add tint to current windows to improve efficiency
E.) Replace all the duct work and A/C's with high SEER rating
F.) Do none of the above, replace the AC's with 13/14 SEER accept the higher monthly utility bills (which would be lower than currently since even basic units would be better than what I currently have).
G.) Other? Open to suggestions.

Thanks for the advice!

---

First thing; ( D ) buy some window tint for $100 and DIY, that will help fast & is easy/ no investment.


- If you would like a trusted Foam Guy in B/CS and/or an Energy Efficiency Consultant I can send you info. A manual J will not do much good, a full blower door test would only really give a great answer. But if you get an A/C unit with 2 speed/ Inverters one can usually be wrong my +/- a ton on equipment.

Pro Tip; If you get foam, get a 16 SEER+ A/C with multiple speeds and worry less about Mold / Humidity. Single Speed A/C units need to be matched perfect with Foam and Heat Loads change over the year and over time.


- Windows; usually very expensive to replace, and often give the lowest ROI vs. most all other IRL ( I've studied green building and windows seem like the easy answer, but IRL they might cost $10-20k and won't have the impact / roi as $3-4k in foam.. not by a mile.
( single panel from the 70's makes it not a bad decision; future homeowner will like) Also ~8 to 12 week turnaround times pre-covid, can be done during slow times. Only a handful of ppl in BCS for windows


- A 'Good Foam' guy who works well with a good HVAC guy is a combo if you're getting foam. Foam can also be pumped into exterior walls. Foam is likely the to give the best ROI, but needs A/C Systems changed in the process ( it also changes the soffits and gable equation as well). Most Foam guys only want to sell Foam and don't worry about how it changes the entire home.

Pro Tip: If you buy Foam insulation , money is often saved on the replacement A/C unit. Often enough to offset the Foam


- Def Replace all the old Air Ducts , no matter.

- Best ROI In Real Life is and always has been a roll of Aluminum Foil over all the windows.. pay no contractors and make someone in the HOA's head explode. The Fine arriving in the mail shortly thereafter might likely cost more than the Foam however.

No HOA but pretty sure my wife would be less than thrilled with foil

I have an interest in the spray foam since the attic is already pretty much not vented. Agree with getting it done right though. Once closer to being actionable I would like your foam guys contact info. Thx

Can you guys that have done tint on windows explain a bit more? Cost, where to buy and how to install?

Seal around supply vents and add more attic insulation is probably best bang for the buck.

As a contractor, I'd recommend stoat foaming the attic. Just venting it better is the cheaper option, but you've still got poor insulation barrier between the heated space and the attic. Extra insulation in the ceiling will help, but spray foam will help drastically, offsetting cost of the ac unit in tonage as well as monthly energy costs.

New windows will make the most difference too. Even if you don't do them all now, do any big ones, west facing, ones that get the most sun if you can't do all now.

I would not tint over new windows. New windows will already have a low e film in them, helping reduce heat transmission. Tint can cause issues with new windows, depending on the type of film, etc. I'd start with windows only and see what the difference is. Solar screens would be the next step before a tint in my opinion.

When looking at AC, step up to a variable speed if possible. This will also save a lot of money in the long run over a traditional single speed unit.

If in BCS, I'd be glad to take a look and give you my two cents, whatever that's worth. I live in a 1950's house, original was 1000sf, we added on about 8 yrs ago. Have done several improvements to help fight similar issues, though our windows are not huge like yours are, we do have a crawl space though instead of a concrete slab, which would be more helpfu. It's definitely a fight when the outside temps are 100+!