Indoor temps exceed outdoor, house cannot regulate temperature

[Inefficient]

Maybe this isn’t exactly an HVAC question, but someone in here may have suggestions. Basically today was a great example, 70* outside, didn’t run the A/C but opened windows as the sun was going down and the indoor temps rose to 81*. When it was 81* inside at 9pm, it was 68* outside. Finished basement temp was 67* all day with no cooling. There was a very cool breeze coming in when I opened the windows and it didn’t do a thing so gave in and ran the A/C. Temp got to 73 in about 30 minutes. But if this were a July afternoon the A/C would be running and running to get to 72-73*.

Raised ranch built in 91, faces sun with no shade. Located in Massachusetts.
When the outside temps are hot enough for A/C it takes an eternity to bring the temps down. The inverse happens in the winter, even though the thermostats read 68-70* with the heat on(forced water) it still feels very cold. I can’t believe how much the outside temp influences this house, it’s always either too hot or too cold. We had a short power outage the other day so no heat for about 40 minutes, it was about 50* outside and the indoor temp fell from 68 to 62 in that short time....and it felt way colder than that I put a jacket on.

Sometimes I feel like I can smell the attic in this house when it gets hot out leading me to believe I’m missing a huge air gap to the living space but I haven’t found anything yet. Attic floor is insulated and has soffit and ridge vents.

Air handler is in the attic. I have the humidity under control when needed with an overkill sized Santa Fe upright in the basement.

Any thoughts on where to start would be appreciated.

 

[WorthFlorida]

Are you the original owner? Did it always work as you describe? How old is the AC unit? If it was 1991, time to get a new one. The new units are incredibly more efficient. Is it an R22 and the SEER rating maybe a 10. New units must be SEER 14 but SEER 16 is more efficient and does not much more in cost. R22 is no longer allowed to be imported to the USA and what is left in inventory is extremely expensive. What is the size of house and size of AC unit in tonnage. If not the full model number will tell the BTU"s.

When you go to a doctor what is the first thing the doctor's office does? Check your temperature and blood pressure. Same as with AC units.

Without a pressure reading it is a guess. With a bad fan or blower or blocked filter it can be diagnostic without gauges but I don't think you have a blocked filter or a bad fan. Outside temperatures have a big play in the pressure readings and AC techs will compensate for the ambient air temperature. Most like them to be well over 70 degrees. On the outside unit there is a chart glued on the inside of the access panel and will give pressure reading in relation to the ambient air temperature.

With northern states with cold winters, the number of hours used per year are far less than say in Florida. I use my most of the year. The problem in cold winter things shrink and it is possible the little refrigerant leaks out. It may take ten years before the performance is noticed but it never hurts to have it checked every five years.

The basement was cool because the ground is still quite cold from the winter.

 

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[Fitter30]

House temp rose to 81* from radiate heat sun load. House cooled off so quick because it was 68* outside no load verses if it was 85*. Contact your electric company see if they offer a energy audit with a blower door test this test sees how air tight the house is. Also look at your windows and insulation. Since air handler is in the attic the duct work might be compromised and might need to be inspected which would be a question for whoever does the energy audit.
You tube will have video on audits.

 

[Inefficient]

Thanks for the reply, that A/C actually works fine, I’m more trying to figure out why the temperature swings in the house are so big. Right now it’s 65* outside at noon and 77* in the house. A/C off. Any house I’ve lived in before at 65* outside just open some windows and get a breeze going.

I was referencing the A/C not keeping up when it gets up into the 90’s simply because the house takes on so much of that heat inside. I’ll throw some gauges on it anyway, but I’m also just looking for ideas on why the house heats up so quickly with the outside temp changes. It also doesn’t cool overnight. Left the A/C off last night, it rained and got down to 55* and woke up to 71* inside....was 73* inside when I shut off the A/C off last night and went to bed so only 2* lower inside and 20* cooler outside + rain. But like I said the other day with a short power outage and no heat for a short time, temps dropped like a rock. So the problem goes both ways on heat and cooling, and the heat is a separate system being forced water so it’s nothing mechanical.

 

[Inefficient]

House temp rose to 81* from radiate heat sun load. House cooled off so quick because it was 68* outside no load verses if it was 85*. Contact your electric company see if they offer a energy audit with a blower door test this test sees how air tight the house is. Also look at your windows and insulation. Since air handler is in the attic the duct work might be compromised and might need to be inspected which would be a question for whoever does the energy audit.
You tube will have video on audits.

Thanks I was going to do my own blower door test also, make something up with plastic and seal it off...I have equipment that pulls 3500cfm and a crazy static lift and I bought a smoke pen to see if I find anything but that’s my one and only idea.

 

[WorthFlorida]

The position of the home to the prevailing winds does make a difference. My last 2 story home faced east and west and on some of those beautiful cool days in S. Florida, my house would never cool off with winds from the north or northeast. I had to strategy open certain windows to get a draft to help cool plus I did get a lot of heat gain from the attic. My current 2 story home in Orlando faces north and south, better insulated house and I can get a pretty good breeze through the house and with less sun that hits the windows. My electric bill is about 30% less than my last home.

 

[Inefficient]

So I’ll do some research also but any suggestions on combating the heat from the attic?

 

[Jadnashua]

Homes built today are required to have a higher R-factor of insulation. Many people tend to go with a black roof shingle, which doesn't help much, either. There's one company, show just this week on This Old House, that has pioneered an asphalt shingle that can reflect as much as 40% of the IR energy. You can probably watch that on the PBS website.

If you have access to the attic, I'd check the type and thickness of the insulation, make sure that the soffit vents and roof vents are not obstructed, and consider adding more insulation. One thing that can help is a different roof. A typical asphalt roof absorbs nearly 92% of the IR heat energy of the sun, and that can make the attic air temperature, and the decking get to over 140-degrees. It heat soaks the insulation and the structure, and radiates it down into the home. Insulation just slows that heat transfer. On the other end of that, an aluminum roof that looks like wood shakes (has an air gap underneath it to minimize conductive heat), will reflect nearly 92% of that heat. A friend put that up on his home, and noticed it felt much more comfortable when he got home from work that first day.

While not as good, since the roof deck will still get hot, would be to put a radiant barrier on the underside of the roof rafters. That would reflect a lot of that heat back up into the roof deck, keeping the insulation cooler, and reducing the heat load. Many of those can be just stapled up to the bottom of the rafters. In the winter, any heat that leaks into the attic tends to also get reflected back into the home. I put some in my place, and in the summer, there was an immediate difference during the day. The ceiling went from being warm after the sun was up for awhile, to being the same temperature as the interior walls.

Your wall insulation may not be all that great, either. There are ways to improve that without tearing up the house much, if at all. Depends on what's there, the wall finish, or whether you have vinyl siding (it can be done from outside by taking off a few strips of siding, cutting some holes with a holesaw, and blowing in insulation, plugging the holes, then replacing the siding).

 

[Reach4]

Located in Massachusetts.

Air handler is in the attic.

So I’ll do some research also but any suggestions on combating the heat from the attic?

Air handler in the attic in Massachusetts? Is that unusual? In an older attic, you would usually have a vapor barrier near the ceiling of the floor below. Then you would have insulation above that. Then you would have a lot of ventilation above the insulation, keeping the attic from getting too hot. If you have an un-insulated air handler, and poorly insulated ducts, in an unconditioned attic, that will not perform well.

I would start by getting an electronic thermometer with an outdoor sensor, and put that sensor in the attic. That is cheap and quick.

Now you have an air handler up there. How does that fit into the picture? I think you need analysis of a professional to understand what you have and what you need. Is the air handler in an insulated enclosure in the attic? Has your attic been retrofitted to be a conditioned space (roof and eaves insulated, no insulation at the attic floor, and no ventilation)? Probably not, because that is expensive to retrofit.

 

[WorthFlorida]

In the NE States adding AC is usually in the attic unless you have a forced air heating system. Attic install allows easy installation of ductwork especially if it is a 1 story ranch. My parents home on LI, NY had central AC installed around 1995 and it was placed in the attic.
Problem here for Inefficient is if the AC was installed in 1991, the duct work is usually undersized for today's modern high efficient AC units.

 

[Taylorjm]

Your issue is the exact reason I installed a whole house fan in the upstairs hallway. When the outside is cooler turning on the fan will pull the outside air in real quick and cool things down fast. The difference between when the fan is on compared to off and the air flow coming through the windows is night and day. Like you though, when it's evening the west facing part of the house gets hot fast so we have to shut those windows and use the north/south facing windows and the attic fan until the sun goes down.

 

[Jadnashua]

Whole house fans can be great for reducing the inside temperatures, but can be a major problem with dust, pollens, air pollution, and allergies, depending on where you are. If the humidity is low enough, evaporative air conditioners function as a whole house fan, too. The nature of their water screens helps remove a lot of the dust and pollen, but do require replacement periodically. A filter for a typical whole house fan just doesn't work, since you need to generally open windows to make it work. Should keep bugs out, but not much more!

 

[Taylorjm]

Whole house fans can be great for reducing the inside temperatures, but can be a major problem with dust, pollens, air pollution, and allergies, depending on where you are. If the humidity is low enough, evaporative air conditioners function as a whole house fan, too. The nature of their water screens helps remove a lot of the dust and pollen, but do require replacement periodically. A filter for a typical whole house fan just doesn't work, since you need to generally open windows to make it work. Should keep bugs out, but not much more!

They actually make filters that are expandable and are about 7"-11" high to fit in your windows with a tight seal and will filter out over 90% of pollen and dust that would get pulled in with the whole house fan. They seem to work good. https://nordicpure.com/collections/window-air-filters

 

[Jadnashua]

Okay, but who wants to go around and put filters in the windows each time they want to run the fan?

 

[Taylorjm]

Okay, but who wants to go around and put filters in the windows each time they want to run the fan?

We leave them in for the spring and fall until it becomes a/c weather. To remove or reinstall is as easy as opening or closing the windows. We only have three, one in each of the bedrooms so it's not like every window in the house has them.

 

[Dana]

Where to start....

Air handlers & ducts in the attic above the insulation is a terrible idea, even in not so blistering hot MA. It punches a bunch of holes in the pressure boundary of the house (the attic floor), which allows humid conditioned-space air to convect into the attic to be taken up as adsorb in the structural wood during the winter. Even if the ducts are tight and the duct boots are perfectly air tight to the ceiling gypsum (something I've never actually seen in a MA retrofit), the convecting cold air out of the cooling registers in winter can be a comfort issue, and sometimes even drips condensed moisture. During the cooling season having it all in the attic adds 1/2 ton to 1/ton of parasitic load, robbing the system of efficiency.

What is the nameplate BTU of the air conditioner, and how big is the house?

A typical 2500' house in MA would have a design cooling load of about 20-24,000 BTU/hr- add 6K for the parasitic losses of the ducts and it'll be in the 25-30K range. (A raised ranch with half the lower level below grade with the below grade wall insulated to current code minimums would usually be under 20K if it doesn't leak tons of air.) But most houses that size seem to have 4-6 tons (48,000 - 72,000 BTU/hr) of equipment installed, which is how it can drop the temp 10F in a half-hour, but since it runs such a low duty cycle it doesn't handle the humidity very well (ergo the whole house dehumidfier). If it were right-sized it should have run pretty much continuously this afternoon, since temps in most of MA (outside of the coastal areas) came close to or exceeded the 1% outside design temp today.

If you want to know what you oversize factor is (parasitics & all), measure the duty cycle of the system tomorrow afternoon (27 May). If it's running less than 75% of the time during the peak heat hours it's too oversized for optimum comfort. Oversized systems result in poor cooling at the far end of the duct runs, and lousy humidity control, with much higher overall temperature swings.

FWIW, I live in a ~2400' 1.5 story house ( + 1600' of insulated basement) with a 5 ton AC system serving a <2 ton load- it cools the place, but it's pretty sucky from an overall comfort point of view. At least the ducts are all indoors, in side the insulation & pressure boundary of the house (for a much lower parasitic load adder.) The thing is about 25 years old, and I'm half hoping it's going to fail soon (careful what you ask for, eh?) so I can install a right-sized heat pump instead, but it has seen so few operational hours in that time it'll probably keep going until I'm just too fed-up and scrap it.

If the temps in your house can drop a full 6F in 40 minutes when it's a fairly temperate 50F outside the place probably leaks copious air, with the warm air headed out the attic, sucking in outdoor air into the lower level of the raised-ranch. Leaky AC ducts & duct boots may be contributing to that problem, but it's probably only half the story- in 1991 leaky recessed lighting was still pretty popular, and there are likely flue/plumbing/electric chases that need sealing too, at both the bottom & top. The upper floor ceiling plane is half the story- the leaks into the lower level are also important. The "stack effect" pressure is defined by the vertical distance between the highest leak point and the lowest- the stuff in the middle hardly matters.

Unless it's a walk-out with a lot of west-facing windows, the basement always has the cool slab keeping summertime temps bounded, and in the winter a constant background heating load. Subsoil temps in MA are in the low 50s, and an uninsulated slab will often be no warmer than 60F even when the heating is running.

My mostly below grade basement with insulated walls and few windows never drops below 65F in winter, heated by the parasitic losses of the (unisulated, antique) ducts and jacket losses of the boiler & water heater. In the spring it can drop to nearly 60F due to the cold slab, and the low duty cycle of the heating system. It's about 63-64F there right now, 82F outside, with the first floor thermostat keeping it 74-75F. (I could keep it 60F, if I wanted to, with such a beastly oversize factor.) The low duty cycle on the AC keeps the ~400 square feet of conditioned space on the upper floor 5-7F warmer than the first floor, being at the ends of the duct runs, and worse than code roof insulation (full dimension 2x6 rafters, cathedralized head-banger ceiling) for higher roof gains.