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Old house ventilation

joneill's picture

I purchased a farmhouse, circa 1890, about two years ago. My 1 year old daughter sleeps in the attic. In the summer, it is sweltering up there, and my 6000 BTU AC unit doesn't quite cool it down. The house has a silver painted tin roof and no soffit vents. I was wondering if a cupola on the roof and soffit vents would make a huge difference in the temperature. Can one add ventilation to a house that was not designed to be ventilated? BTW, the walls are two feet thick, so I don't want to use a gable vent

(post #175268, reply #1 of 7)

Your house sounds like a great adventure! I have no answer to your question but in the interim can speak for experience that fans work wonders, even one overhead on low can reduce the temp by at least 10*. Consider adding some plants, too.

(post #175268, reply #3 of 7)

This room has a sloped ceiling. For the fan to clear the walls/ceiling the fan would be about chin high.


What's up with the plants? Do you mean to shade the outside of the house, or do they have a cooling effect on the inside?

(post #175268, reply #5 of 7)

The plants will work inside or out in helping to cool the room, but especially on the outside. It's very easy to prove outside - isn't it cooler under a tree? Inside it’s more subjective.<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />


Look for tiny portable fans that you can attach here and there with their clips. If you don't believe it, try just one and check the temp. They are dirt cheap – I’ve seen them for 6 bucks and you can aim them and adjust their speed. Keep one or two running on low and the noise will soon “disappear”. Also you might consider keeping the door closed if the heat from below rises.


Do you suppose that the heat is leaking down in from the roof or walls more than rising from below? If so, I wonder if the indoor ceiling could be lined, even partially like a canopy, with some sort of refracting “space fabric”? A ficus or jade or whatever is an easy indoor plant for you can work on the hot wall. You could add a fountain if the heat is dry, and the bubbling noise will also help to disguise the fans.


I hope you find a suitable solution before summer hits or that you have a cool summer, and see if you can get a thermometer for that room that is not in the blow of a fan so as to give you a false impression of the entire room temp, and that you can monitor from elsewhere. Hope that makes sense….

(post #175268, reply #2 of 7)

Two feet thick?  Stone, straw bale?  I assume that the 2' material is in the gable ends, thus your comment.


Ventilation is a black art.  Lots of discussion about this one.  On the surface, a cupola makes perfect sense.  Air in thru the soffits, and out from above.


Do do a little research on the size of intake vs the cupola tho.  Maybe multiple cupolas.  Check out  the old cavalry fort in Ft. Davis Tx.  Always seemed an elegant solution to me.  Also the colonial houses in Mexico.  5 meter ceilings with their version of cupola on top.  Great chimney effect.


ShelleyinNM

(post #175268, reply #4 of 7)

To beperfectly honest, the house has aluminum siding on the outside, and I'm terrified to look behind it. I do know, from all the pieces around the foundation, that it was originally stucco, but I don't know what the stucco was applied to. Either log or stone I would imagine. I do believe the house would look great with a cupola, I just hope it takes some heat out though. Thanks for responding.

(post #175268, reply #6 of 7)

Is a ridge vent an option? Then you apply insulation with baffles that lead the heat up to the vent.

There is thermal paint made for the room side of the roof. Keeps a lot of the heat from entering the attic.

Janet

(post #175268, reply #7 of 7)

I just solved a similar problem in our house.  Without adding insulation.  Without adding any fans or vents.


Before I fixed it, the second story rooms (of a 1-1/2 story renovated house) were unbearably hot in the summer (even with both skylights and both large windows fully opened).


Before attic work completed (2 weeks ago):

        Outside temp:           21C (70F), sunny, 2pm

        Ground-floor temp:      22C (72F)

        Side-attic temp:                39C (!)/ (102F)

       Second-floor temp:      28C (84F) with all windows/skylights open, 34C (92F) with all windows closed.

 


 

After attic work (since last week):

        Outside temp;           21C (70F), sunny, 2pm (same)

        Ground-floor temp:      22C (70F) (same)

        Side-attic temp:                39C (102F) (same)

        Second-floor temp:      23C (74F) with all windows/skylights open, 28C (84F) with all windows closed. -- a 5-6C (10F) drop!

 

No insulation was added.  My approach was to install/reconstruct an air barrier so that there is a continuous air barrier plane around the entire second story. 

 

I installed custom-cut pieces of plywood in every floor joist cavity, just below the pony walls.  Foamed around the edge to completely stop any air from moving from the side attics to the space under the second story floors.  Building envelope theory 101.

 

Basically, the 2 story (uninsulated) floor was freely exposed to the attic air.  So it's as if there was a 500 square foot, uninsulated surface (the floor) between the 39C (102F) attic air and the inside of the living space.  So lots of heat movement into the house.  Square-footage-wise, it's as if there were no insulation at all in our house's roof!

By extending the pony walls all the way down to the first floor ceiling, the hot attic air is now no longer able to reach that uninsulated 500 ft2 floor.  So now the heat has to force its way through the (already insulated) pony walls.

Make sense?

 

Total cost:

        2 sheets of 5/8" exterior plywood @ $35 CDN each (=$70)

        2 boxes of 2" drywall screws @ $3 CDN each (=$6)

        4 cans of foam (2 low-expansion window/door foam; 2 high-expansion crack filler foam) @ $11 CDN each (=$44)

        -------

        $120 CDN

 

The difference in comfort level is unbelievable.  Now that there is only a 1 degree difference between upper and lower floors in our house, it's startling just how more usable our upper floor is.

 

Hope this helps,

.../j