How to ventilate upper floors (no attic)?

11 years ago

Hi, I hope someone can help me here. I live in Europe in a concrete construction 2 story townhouse (attached on both sides to adjoining townhouses, so we only have windows on N/S exposures). There is no attic, rather a flat rooftop deck above the second floor. The second floor gets extremely hot as the day goes on and all the heat rises and gets trapped. I keep all the windows open at night when there is a gorgeous cool breeze, but the cool air barely gets in and only by morning has the heat finally dissipated. I have tried asking local contractors about some type of ventilation/exhaust fan for the second floor, but either due to a language barrier, or different methods of construction here, no one has any idea what I am talking about. Growing up in the US I remember having an attic fan that sucked up all the heat and ventilated it outside, but is there such a solution for a home without an attic and with concrete walls?

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Comments (5)

mike_home
11 years ago
I grew up on the second floor of a brick house under a flat roof. I know how hot it can get.

Put a fan in the window and have it exhaust to the outside. It will help draw cool air from the other open windows. Any type of box fan will work as long as it doesn't fall out the window.
ionized_gw
11 years ago
Are you in a very dry, sunny zone or cloudy and wet? Either way, you seem to be getting lots of re-radiation of heat from your concrete ceiling. What color is your roof coating, dark or light and reflective? You might want to make some changes when it comes time to revise the roofing material. Reflective roofs absorb less heat, but they also give it up slower.

Ventilation by drawing air out alone might suck relatively warm air up from the lower level. This enhances the natural stack effect with open windows on the upper and lower floors. This is an efficient way to cool from an energy use standpoint, but will delay cooling of the upper floor. To get the quickest cooling upstairs when the outdoor temp is good, you should probably have a blower for intake and one for exhaust. This is unless you can effectively close off the upper level from the lower.

The only way to install these other than in windows will be to knock holes in your walls or roof.
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Well, idmd, this is just my opinion...I grew up in a one-storey ranch house built in 1958, the roof was hipped but fairly shallow and my dad put insulation batts in the attic, but I'm pretty sure it wasn't up to modern code. This was back in '61 when we moved in, and lived there until '87. We never had moisture problems and had no ridge vent and I don't recall any soffit vents either, although the crawlspace had sliding louvers every six feet or so. My current house is a 1908 two and a half storey frame house with a steep pitched hipped roof with three dormers and two chimneys. It has box gutters, so no soffit vents, and no ridge vent either. There is not one sign of moisture damage in the attic, which is a finished single room which takes up all the territory except for about 5 feet per side for storage under the rafters. The roof is skip-sheathed which meant original roof was slate, but is now asphalt shingles. My guess is that if it has lasted this long without vents, it will last another 100+ years. Old houses, even ones built in the 50s were not so hermetically sealed that moisture was a problem. The biggest problem with moisture from our ranch house was in winter, when ice formed on the aluminum window frames and the marble sills. We tended to put towels on them to catch the water as it melted--this was in the bedrooms, at the far end of the house from the furnace. :)
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A gable fan would be hard to install because the gables are up there behind the ceiling and walls. The only access to the eaves are the kneewall doors and there isn't much space behind them. We'd have to cut the ceiling to get up there to the gables. The extra roof is an interesting idea. Would the sleepers run up and down the roof and create the pathway for the air? Or would they go across the roof? If they go across, wouldn't they then block the air pathways? Would the extra weight of another roof be a possible problem? How could I tell if the structure could handle sleepers and an extra roof? The present roof sheating is 1x4 boards, not plywood. I'm told there are some soft spots and some of the sheating is likely going to have to be replaced. There was a leaking problem in 1998 and roof repairs were done then, but I don't think they did anything to the sheating then. Can baffles be put in from on top the roof after the top is cut off for the ridge vent? Could they slide in from there or do they tear up too easily? Are baffles ever made of anything besides foam? The house has been there 56 years and the present roof has lasted 29, all without roof ventilation except for the gable vents, so I'm wondering why a new roof would start to have problems because of lack of ventilation. It's a pretty steep roof, if that makes any difference in this issue. I'm going to use a light-colored shingle. There are mature shade trees in the yard, and one in particular shades it from the west. Virginia is hot in the summer, but in the winter it seldom gets below 20.
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Unless the roof or pipes leak or ducts discharge into the attic, during hot humid weather moisture can get into an attic through oversized wall vents that allow moisture laden air to enter the attic and/or from a bathroom directly below the attic floor. Moisture from a bathroom can be controlled with an exhaust fan and a vapor impermeable ceiling paint. Moisture from vents can be reduced by substituting smaller eave and ridge vents In a sealed conditioned attic with a moisture barrier at the ceiling of bathrooms, moisture is not expected to enter the attic but if it does the conditioned air should dry it. Even HVAC ducts in the attic will leak enough dry air to keep the space dry. These issues can be solved regardless of whether the attic is vented or sealed so you should decide what you want, then design the attic. Since it is expensive, the primary reason people seal an attic is to allow HVAC equipment and ducts to be located there but they might also want to achieve a higher R value without changing the structure or the create a better environment for storage. If you are planning to replace the roofing I recommend applying Grace Ice & Water Shield over the entire roof surface and using coated aluminum or copper step flashing at side walls.
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Hello, The potential issues all depend on how the roof was constructed and also insulated. Assuming the interior ceiling isn't vaulted I'm going to assume their is insulation on the attic floor. Yes, I know you said you have no attic but I think what you mean is that there's no accessible attic space. But unless you're vaulted, there's an attic space. You don't have to ventilate an attic space if it is completely sealed off. Meaning, no roof vents, etc. There's always the potential of condensation building within the attic during hot summers but that damage would be caught during inspection. My guess is that at some point after the home was built they drilled those holes into the attic space to minimize that condensation and it's probably doing an okay job unless you see any leakage/drywall damage on any of the ceiling areas of the home. I don't know Virginia climate as much as west but I'm going to assume it's more humid in the summer so that's your real challenge. There's a lot of varying information on how to ventilate or not ventilate an attic space - so you'll just have to talk to a couple experts on site. I say put an offer in and find a good home inspector that you personally meet at the site to evaluate your concerns. Those guys love to find issues with homes and maybe there is none but that's your best route. If your inspector seems perplexed, find another inspector. If there is a problem and you can put a number to altering the space, the homeowner will have an opportunity to fix the issue. I realize this adds time and stress into the process but will be worth it. The RE agent should make sure there is an inspection deadline and resolution in the purchase contract so you have an 'out' if nobody agrees with inspection/remedy costs, if any. Good luck! Jonah
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energy_rater_la
11 years ago
as a child we had a big fan that my Dad would
install on a centrally located window. he would
install it to exhaust out. we would sleep with
the windows open & the fan would cause the
outdoor air to be drawn inside.
it was wonderful..esp with wisteria outside
my bedroom window.

now I know that this big fan was originally
an attic fan adapted to fit on outside of window.
because the fan was so large it really
moved some air, much more so than a
regular box fan.

would something like this work for your
second story??

best of luck.
fooglie1
Original Author
11 years ago
Thanks for the replies. Yes, we live in a dry, hot, sunny location. I've looked for window fans but haven't found any in local stores. Part of the problem is that the windows in my house are not double hung windows, they are slider windows, so even with the window open I don't have a wide space to set up a window fan (although maybe I could put them in vertically?)
I am willing to invest into installing something permanent on the rooftop but don't know what to look for. Are turbine vents/whirlybirds going to help me? Can they be installed on a flat concrete roof?
ionized_gw
11 years ago
What is the upstairs layout? Is there a central hallway? If so, would you be able and willing to leave the doors open to the bedroom(s) so air can be drawn into all the room upstairs via their windows?

A pedestal fan next to the windows might help, but it will be the least efficient of all your options.

A modern version of your old whole-house fan would work, but you would have to build a new roof over it. Is the climate mild enough that you don't need much heat and you don't cool? If so, you don't need much air sealing. These fans are designed to seal up well when not in use.

Use care to prevent back-drafting of combustion appliances when using whole-house vent fans.

Here is a link that might be useful: whole house fans and other vent devices

How to ventilate upper floors (no attic)?

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mike_home

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How to ventilate upper floors (no attic)?

Comments (5)

mike_home

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