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My condo had air infiltration from gaps between the baseboards and hardwood floor that was reduced by caulking. Electrical outlets also leaked; thin insulation can be inserted behind the covers.

I have a large skylight which made the condo miserable in summer until I applied insulating window film to it. If you have south- or southwest-* facing windows, consider adding awnings or outdoor shades to shield them, or applying low-SHGC** window film.

*southwest-facing windows are the worst during the summer as sun blasts through them from noon to sundown

**solar heat gain coefficient

Add insulation and shade.

Without knowing all the facts, installing ceiling fans may help.

Thank you all for your ideas. We live in a single family home that is 2 stories plus a finished basement. The basement always stays cool since it is underground with concrete as the exterior walls.
Our home is east-facing so we mainly feel the scorching heat in the afternoon since the west side of our home has large windows on the main level and second story. We do have ceiling fans in all the upstairs bedrooms, which help a little.

I also was curious about your thoughts on a 2.5 ton unit for a 2900 sq ft home? What is the proper/ideal size? A second unit is an interesting idea, but I don’t believe our neighbors have this problem since they have a single unit installed by the builder.

" about your thoughts on a 2.5 ton unit for a 2900 sq ft home? What is the proper/ideal size? "

Needs to have a "manual j" test done. Basically they engineer the system for the house. Impossible to tell beyond a WAG with the info provided. And honestly you already have gone down the WAG rabbit hole.

You have an up to $7000 budget to test and improve the energy efficiency of your house. Plus, the improvements will continue to supply savings going forward. A blower door test can show you air infiltration. The right assistance could allow you to avoid replacing the unit. Your utility company may be able to suggest contractors with the expertise to improve things. You have a pretty big budget. A terrible Blower Door score till we figured out the problem! - YouTube

Are there cold air returns from the upper story? Does your attic have proper ventilation? is the attic venting optimally sized and correctly installed? Do you have enough insulation in the attic?

Uncovering the partially blocked gable vents (covered by a previous siding job), and installing a roof vent, made a difference in my old house, as did adding Reflectix heat barrier insulation to the attic rafters..

"we mainly feel the scorching heat in the afternoon since the west side of our home has large windows on the main level and second story"

I'd tackle that problem first.

Window film examples:

• 3M Sun Control Window Film Prestige Series
• Llumar Spectrally Selective Window Film
• Avery Dennison Spectrally Selective Window Films

Two stories will never feel comfortable with one unit and no zoning. As to the tonnage we don’t know how high your ceiling are, how well you are insulated, etc.

Just curious how you add zones after the fact? Can someone explain this process? We have a similar heating conundrum which will create a cooling one when we finally get AC

2.5 tons is not a lot of cooling for 2900sf, but it depends on your climate zone. It needs 4-5 tons where we are in California.

We had one room that was too hot in summer and too cold in winter and we had the attic insulated and then added an extra vent to the room and that helped tremendously.

When I bought my one story house, I had two 5 ton units installed for 3900 sq feet. I’ve added square footage and two more smaller units. But I live in a hot state. If your summers are pretty hot, I can imagine the upstairs cannot be adeqately cooled. Maybe get a second opinion from another hvac company?

I appreciate all your comments, thank you ! I will do some research about all your suggestions and go from there. Hoping for a cool summer this time around! We live in Colorado, 40 minutes north of Denver, so the summers could get pretty hot! Thanks all!!

2.5 tons is probably too small for a 2900sqft home unless it is super-super well designed and insulated. Did the builder install only a single 2 ton in the other similarly sized homes in your development (or was it 2 tons upstairs plus 2 tons downstairs?)

@sktn77a just 1 unit is what the neighbors have if they opted to go with the builder’s installation.

csb you still haven't answered what size units neighbors have that are happy with heating and cooling. I don't understand why you didn't install hvac during construction. Where is the unit located and how is it ducted to other floors? I'm with those above who say installing a second unit is more sensible than up sizing a single unit.

Just curious how you add zones after the fact? Can someone explain this process? We have a similar heating conundrum which will create a cooling one when we finally get AC

West Coast Hopeful,

Zoning (via controls) isn't a fix for an otherwise failure of a system(s) - zoning a single system is (more or less) the incorporation of controls designed to run the system from more than one vantage point. (2 or more thermostats in the structure)

Zoning will not increase the operating size (tonnage) of a system. So if the unit is too small it will be too small then with a zone system attached to it. The zoning if done properly in a world that doesn't understand what proper is (gets triggered when you point that out) well?

Zoning via controls is a tool in the tool box. My opinion is that a zone system isn't necessarily a good idea for just any structure. Zoning with the use of controls should be elegant, if that can't be done even more trouble is likely to follow.

Zoning controls are made by an assortment of companies (majority of it is garbage), some zoning is manufacturer specific meaning it was designed to control a specified branded box (proprietary controls - proprietary signals).

As time goes on after circa 2022/2023 zoning may become even more difficult due to the proliferation of communicating equipment that typically use proprietary signals to run the equipment.

If you don't like change you are in the wrong place. Or at least that's what they tell me.

Asside from all the possible changes coming down the HVAC road... if the structure makes it impossible to implement a zone system elegantly it's probably not going to be worth the trouble via the controls only method. Maybe something will happen and I change my mind? My crystal ball isn't always so 'crystal'. Hazy check back later sort of thing.

Elegant? if you think you can just cram all this stuff in a closet with no access. (A common theme among builders if you catch my drift)

------- zoning via equipment ------

yeah you can also zone with equipment. This is typically by floor of the structure. 1 HVAC system for the down stairs - return and supply ducts to that floor only. 1 HVAC system for the up stairs - return and supply ducts to that floor only. Thermostat on each floor to control system for that area.

---- no ducts ----

mini split realm where heads are placed on the wall of the room(s) to cool. If space is available over head as in a floor with attic space over head a cassette style mini split can be used in the ceiling of the room you are conditioning.

The biggest problem for the mini split realm is much more equipment is needed, which results in more maintenance, more repairs, and eventually more replacement costs.

I service the Katy, Texas area.

Hi, csb,

Depending on your municipality, tract home builders may have the option to submit a single set of plans and specifications for a model home that will be built on various lots. This shortcut fails to consider that homes can have significantly different cooling loads depending on the home's orientation and solar heat gain. Replicating what works in your neighbor's home may not yield acceptable results in your home. Your A/C system needs to be designed for your particular home on your particular lot.

You'll be best served by having a design professional calculate the cooling loads room by room, and then consider whether and how to integrate your existing system. Many utility companies offer free energy assessments for their customers and provide access to professionals who can help. You might start by giving them a call.

@Austin air if someone has an undersized system and not space to expand it in mechanical room what could they do then? Mini splits are an aesthetic that changes a room big time.

" A couple of years ago, we purchased a new tract home "

@User, no chance of "should have been caught at the beginning of the design"

Do you have window coverings and use them? we close all the shades when it’s hot and direct sun is shining. Spouse considering outdoor shades as well. we don’t have AC so make the best of cooling house at night with open windows and covering windows in heat. Makes a huge difference with no electricity used!

"just 1 unit is what the neighbors have if they opted to go with the builder’s installation"

Assuming the homes are similar, were these 2/2.5 ton condensers (go look if you don't know)?

It’s easy to say make room or who cares about aesthetics from a keyboard. AC is a luxury for many. While growing in trend here in Vancouver it’s still not the norm at all. Most people use fans, window coverings, and open/close windows. Climate change has dramatically impacted summers here in the last few years with exceptional heat like we have rarely gotten previously. So probably many, like me, are hesitant to redo a basement or change how our bedrooms look just yet. While I would love to embark on a redo of my entire HVAC system, somewhat like many folks, it just might not be in the cards and berating the fact it wasn’t done before doesn’t change that. We consider AC every year but so far haven’t pulled the trigger and I have to admit that once the few hot weeks fade I’m often not sad we didn’t do it.

@klem1 thanks for your feedback. Not installing it during construction was a mistake on our end and will definitely choose differently should we build again.
A neighbor we spoke to (recently) who has a comparable sized home shared that he chose to go with a 4 ton unit. He has a background in construction too which definitely worked to his advantage. I will check with other neighbors who opted for the builder install soon to see what they have. The second unit suggestion on this thread is one that we will be considering for sure.

@lharpie thanks! Yes I’ll also be looking into outdoor shades/awnings especially for our sunny afternoons. We do have window coverings but they are panels. I can probably also add some curtains for hot sunny days.

@klem1 the exterior unit sits outside our home on the north side (east-facing home) on the main level and is linked to our mechanical room in our underground basement. I can’t answer the ducting as my knowledge is very limited in this field.

@sktn77a I’m on it!

I think it has been said but not maybe not enough. Outside shading is a ton better than curtains/blinds. A curtain does block some solar gain but an outside shade blocks all solar gain. For less than $7k, you can put motorized exterior covers on large west facing windows.

If you are wanting something less expensive, window tint done DIY is very cheap.

I live in humid NC (and humidity removal takes a good amount of cooling) and have about 1 ton per 1,000 sqft and we sleep at 65 degrees on a 100 degree day and it is still 85 outside when we go to sleep. You should never ever try to size an a/c unit by square footage. We don't need much a/c because ... we have limited west facing windows.

In a dry environment, you can get by with no a/c if you limit solar gain. If you don't - well then you can't. But you don't have to limit the solar gain that much if you have 2.5 tons.

You can certainly add a mini-split for a lot less than $7k if limiting solar gain is not an option.

Totally agree with an energy audit. You might have some easy thing to do (and cheaper than ...) that fixes the problem. Don't assume you have an undersized unit based on what a neighbor has or what someone on the internet says.

@Austin air if someone has an undersized system and not space to expand it in mechanical room what could they do then? Mini splits are an aesthetic that changes a room big time.

WestCoast Hopeful,

Options are few without the room needed for it. If you don't like mini split aesthetic you probably won't like window unit either. Other issues yet to be brought up is noise. If you put equipment in the room you're in and you're trying to sleep --- if noise bothers you --- those are issues that appear on this board quite often. (clicking noises) ---mini splits often start out quiet and over usage and passing of time develop noises on their own as well as other headaches like dripping water and such. So weigh your choices carefully.

If you are able to give up room to accommodate an HVAC change / redesign the cost goes up depending greatly on how much redesign you're needing.

I personally don't care for mini splits either, but in some situations it could be that or next to nothing other than window units. In my area HOA regulations don't allow window units although some people use them anyway.

A less common approach is to use high velocity system that uses 2" ducts. Space Pak is probably the biggest brand I think there is another brand as well in the space of high velocity systems. The cost of this type of unit might would probably be less than a huge remodel project that involves removing walls or putting up walls for that matter, but you will still need some place to put the air handler like basement or attic then snake the 2" ducts (supply & return ducts) to the rooms you're wanting to heat / cool. These are specialized systems for retrofitting older homes (structures without ductwork). I don't know of any distributor in my area that carries them so that is another issue that should weigh heavily on your choice. (long waits to repair it when it breaks).

You can cool a 2900 home with a single unit. I have a 3800 home and use a single unit. Don't know how many tons, but it's the biggest one they sell. All homes in my neighborhood have a single unit. There's one bedroom that my son complains is too hot in the summer, but he has 2 computers running all the time in it, so doubt anything would work. He has big ceiling fan.

If you don't have an attic fan, get one. I have two. One solar and one electric. The solar had a $200 tax credit, so it only cost me about $500. No energy costs ever.

Pardon the pun, but I'm not a fan of powered attic vent fans. Before rushing to install them, you'll be well served to understand the potential downside of doing so. Then you can make an informed choice https://basc.pnnl.gov/information/attic-ventilation-fans

The value of an attic fan is definitely dependent on house design. Generally not desireable even if often thought to be. It can make the attic cooler at the price of negative pressure that pulls conditioned air out of the house. But it definitely is not consistent. I would not recommend without expert on-site advice.

The largest typical unit is 5 tons - so twice the power of the OP. It is not the number of units but the tonnage. Number of units helps with redundancy and it can help with control and duct length but otherwise two 2.5 ton units is equal to a 5 ton unit in cooling power.

A better metric than square footage is west facing window square footage. In milder areas, the wall size isn't that important. I doubt we are talking Arizona or Texas here. The only metric that matters is a manual J of course but for forum advice, the west window area is more important. My house designed for orientation has 50 sqft of west facing windows and a 50 year old oak tree 35 feet due west of the house. My house would be easy to cool even if it was 6,000 sqft.

While powered attic vent fans can pull conditioned air from the home, they can also pull air from unhealthy spaces like garages and crawl spaces. With that is the potential to introduce moisture, soil gases, etc. into the living space, and attic. I'd opt for improving passive ventilation measures.