Have a American Standard central AC unit that is about 4 years old. We have a 1600 sq ft bungalow type home built in 1942 has half basement full main level and full upstairs with no attic. On days that are about 95 or less central AC keeps up well, but upstairs gets to hot so we supplement with a small Kinmore 10,000 BTU window unit. The heat seems to radiate through the roof on hot days even though we have new shingles just put on about 2 years ago that are supposed to be heat reflective shingles are Malarkey brand. Our central was inspected and checked out OK. Have an open doorway at top of stairs so am thinking of installing a door and maybe that willkeep some of the cool air up there. Now that August is here temps and humidity is lower the we do not run the window unit as much. I like to keep temp at about 80, but my wife has thyroid issues andtend to overheat and likes to keep thermostat at about 75. No way to insulate roof since it has no attic. Our 10,000 BTU window unit is probably 10-12 years old so maybe getting a new one would be more efficient.Anyway just wondering if anyone else supplements central AC with window units on hotter day?
using a window AC unit in addition to central AC
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I have been so far this summer. Our temps in the living room were at about 80 from 3-5 pm, when the sun was shining right onto the front of the house and it was about 95 degrees out, we normally leave it at 76. I bought the small GE 5500 BTU for 120$ and its really been helping. Maintains the first floor at the set temp no problem, although we have a smaller 2000 sq ft home. I hate doing this, as Im always a fix it right type of guy, but our unit is from 94, so I know what Im going to be hit with, and with the birth of our son somewhat recently (december) its working just fine for us right now haha.
What size is you Central A/C? at 1600sqft it should be 2-1/2 to 3 ton using the rough rule of thumb of 1 ton/500 sqft.
the 10,000BTU is about 0.8 ton. so add that to your AC needs if you don't change the house at all. When its time for new AC that is your tunnage to keep the house cool on the hottest days.
Also check your attic for proper ventilation and insulation. if the attic temperature is ridiculous hot (mine was 140F) then a power vent may help.
Make sure you insulation is good and thick as well.
Singles will not help much unless they are bright shiny foil.
You can get a IR gun and start scanning the walls and windows to find out where the heat is coming into the house. Look to see if there is a way to insulate that.
the 10,000BTU is about 0.8 ton. so add that to your AC needs if you don't change the house at all. When its time for new AC that is your tunnage to keep the house cool on the hottest days.
Also check your attic for proper ventilation and insulation. if the attic temperature is ridiculous hot (mine was 140F) then a power vent may help.
Make sure you insulation is good and thick as well.
Singles will not help much unless they are bright shiny foil.
You can get a IR gun and start scanning the walls and windows to find out where the heat is coming into the house. Look to see if there is a way to insulate that.
Yes. In my computer room. About 1500W worth of dissapation so I suppliment to central A/C with a 5k btu window. Still doesn't keep up on the hottest days, but I have it set at like 70.
I bet there is something that can be done to insulate the ceiling. It's probably worth looking into if you plan on staying at your house for years to come.
Nick1994
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The problem is 1 A/C unit for 2 stories.
2nd floor is naturally hotter than the 1st floor, and properly ducting the HVAC system is a perfect science that most HVAC guys can't do.
2 floors, 2 A/C units!
But for your current situation, window A/C units are cheap and much more efficient these days than the old ones. Buy a new one to supplement your current system and don't worry about it.
2nd floor is naturally hotter than the 1st floor, and properly ducting the HVAC system is a perfect science that most HVAC guys can't do.
2 floors, 2 A/C units!
But for your current situation, window A/C units are cheap and much more efficient these days than the old ones. Buy a new one to supplement your current system and don't worry about it.
Originally Posted By: skyactiv
I bet there is something that can be done to insulate the ceiling. It's probably worth looking into if you plan on staying at your house for years to come.
That. You CAN insulate a roof without an attic.
Google says so!
I bet there is something that can be done to insulate the ceiling. It's probably worth looking into if you plan on staying at your house for years to come.
That. You CAN insulate a roof without an attic.
Google says so!
you could always get a mini-split.. but a small window unit is inexpensive.. and not as great a theft risk on second floor.
House is a 1.5story cape cod
The upstairs gets over 95f in the daytime from the roof sun.
I could set the downstairs to run continuously and it still wouldnt be comfortable.
So the downstairs gets 74f and I run the window unit that pulls about 450w.. much better solution esp. since my house has a "central collector" type return and no cold air return vents to balance the house.
House is a 1.5story cape cod
The upstairs gets over 95f in the daytime from the roof sun.
I could set the downstairs to run continuously and it still wouldnt be comfortable.
So the downstairs gets 74f and I run the window unit that pulls about 450w.. much better solution esp. since my house has a "central collector" type return and no cold air return vents to balance the house.
I have a De Longhi portable air conditioner that is 14,000 BTU and it helps a lot -- we have the master bedroom downstairs and have 2 central AC units a 3 ton upstairs and a 3.5 ton downstairs. The portable is in the master bedroom.
Having the standalone AC in the bedroom cools it a lot even though the whole house central air is adequate. The trick with a portable AC is you have to insulate the exhaust hose. I am using an R-6 duct jacket (foil tube lined with pink fiberglass insulation) and it works great.
It also lets you set the rest of the downstairs to a higher nighttime thermostat setting.
Having the standalone AC in the bedroom cools it a lot even though the whole house central air is adequate. The trick with a portable AC is you have to insulate the exhaust hose. I am using an R-6 duct jacket (foil tube lined with pink fiberglass insulation) and it works great.
It also lets you set the rest of the downstairs to a higher nighttime thermostat setting.
Sounds like you need a radiant barrier. To install one now wouldn't be worth the cost. You could have had the decking replaced and one installed BEFORE re-shingling. Added cost & too late now.
You can drop the 2nd story bedroom ceilings, install a RB, then foam sheets, then perlins, then 'false' ceiling. It'll be expensive though unless you DIY.
Any 2nd story glass where Sun hits needs at least a solar screen on it. You can also cut 1" foam board with a reflective side to fit 50% of the inner window. It's cheap and effective. I use that trick here for the rare occurance we actually have 'winter' and it's below freezing for several days (low 20's down to mid-teens).
Overall, you need more airflow up top where it's hot. That means larger ductwork & buckets & grilles.
You can drop the 2nd story bedroom ceilings, install a RB, then foam sheets, then perlins, then 'false' ceiling. It'll be expensive though unless you DIY.
Any 2nd story glass where Sun hits needs at least a solar screen on it. You can also cut 1" foam board with a reflective side to fit 50% of the inner window. It's cheap and effective. I use that trick here for the rare occurance we actually have 'winter' and it's below freezing for several days (low 20's down to mid-teens).
Overall, you need more airflow up top where it's hot. That means larger ductwork & buckets & grilles.
I do in my bedroom; I like it cold when sleeping. I want a penguin to feel comfortable if it was to walk in my bedroom at night!
Yes, we have done it for years. All of the upstairs bedrooms have small window units. There was too much of a differential between downstairs temp and upstairs.
Need some high wall or ceiling cold air returns in the second story to pull the heat out of the second story.
Yes, I do! Its a must in my house. I have a 5 story house with the top level being my bedroom and master bath...and full of windows. The lowest level can be a comfy 68 degrees, the main will be about 75-78 depending on sun, and my bedroom will be over 80. So, I run a window unit in my bedroom and keep the door closed. Bedroom is kept at 78 during the day, and dropped to 72 at night. The small window unit has no trouble keeping up if I keep the blinds closed.
Well we do not have an attic, just the ceiling which is pitched like the roof. The ceiling , just like the walls are plaster. I reckon that the ceiling is plaster, and airspace and then the roof deck and then the tar paper and shingles. house was built in 40's so doubt if there is insulation in the roof deck space . rafters are 2x6. About 3 years ago we had the outside wooded siding removed and replaced with composite siding. When old siding was removed our contractor noticed that there was zero insulation, which was not uncommon in the 40's . Did not really have insulation much back then. Anyway we had contarctor blow in wall insulation. inside walls were plaster, then air space, then wood boards then siding over that. Of course with new siding they also put on house wrap which they did not have back in the 40's. I am thinking that the oly way would be to tear the whole roof off and try and add insulation to the space of the roof deck. Probably not worth it. I am 58 and as soon as daughter graduates from college in about 3 years we plan to sell home and move into apartment. we want to travel more and not have to mess with home maintenance. oh we do aslo have a 5,000 BTU window ac as well in a bedroom upstairs as well, but we only run that on days that are 100 degrees which is only maybe 5 or so days per year. Our central unit does fine keeping main floor and basement cool, but on days when it above ohh 95 plus the upstairs just does not stay cool without the window units to assist. for the most part here in lincoln NE that is about mid June to mid to late july. This week is lower 90's and my wife kept the window units off. I am guess that many homes that do not have an attic probably tend to get quite warm, now way to really insulate the roof deck. Yes I cannot really tell how much cooler the reflective shingles are making. compared to last summer maybe a couple of degrees, but not really enough to make much difference, but certainly cooler than dark shingles. though here in Nebraska when it snows tha dark shingles have a slight advantage. Our central AC and furnace was sized correctly for our house by the furnace AC company, but on real hot days 95 to 100 plus it cannot make up for that non insulated roof deck with no attic for air ventilation.Our windows are insulated Pella installed about 10 years ago and never ice up or leak. most of the heat radiates from the roof I think. Our walls are now insulate with blow in, not sure how much that helped. Our electric during summer is about $130 during the hottest time and probably be about $110 -120 for aug and then will drop to probably $70.00 during fall winter and spring.
Yes that may well be as the roof deck rafters are 2x6, but I reckon it would mean tearing down the thick plaster ceiling and then putting in some sort of batt insulation and then putting in drywall ceiling but with only 6 inches of space or less in that roof space not sure what R value I could expect. If we were staying long term maybe , but more than likely we will sell the place and move into sr. type apartment complex after daughter is out of college about 3 years. I think I will buy a brand new 10,000 BTU window unit as our Kinmore is at least 10 years old, new ones are probably more efficient.
Our central AC unit is about 4 years old so still pretty new. Our 10,000 BTU kenmore is probably 10 t0 12 years old our 5000 btu unit is about 3 years old. In the winter I take the window units out. Our 10,000 still blows fairly cold air, but does vibrate a lot more and stay cycled on more than it used to and since it is over 10 years old I likely will get a new one which should be quieter and use less energy. I might even go with another 50000 unit as we use fans to assist in air movement as well. Here in Lincoln AC can last a while since we only need AC maybe about 3-4 months of the year. The furnace gets a real workout and must crank out heat a good 9 months of the year.
Originally Posted By: BJD78
Our 10,000 BTU window unit is probably 10-12 years old so maybe getting a new one would be more efficient.
New window units really aren't more efficient.
Originally Posted By: BJD78
Anyway just wondering if anyone else supplements central AC with window units on hotter day?
I do. Mostly because I want my bedroom cool enough without having to cool the whole house. That and my ductwork doesn't do much for the upstairs A/C since the return on the second floor is at floor level, so it never sucks the hot air back to the air handler.
Our 10,000 BTU window unit is probably 10-12 years old so maybe getting a new one would be more efficient.
New window units really aren't more efficient.
Originally Posted By: BJD78
Anyway just wondering if anyone else supplements central AC with window units on hotter day?
I do. Mostly because I want my bedroom cool enough without having to cool the whole house. That and my ductwork doesn't do much for the upstairs A/C since the return on the second floor is at floor level, so it never sucks the hot air back to the air handler.
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