Best way to cool finished attic

[NuclearNerd]

Hi all

I am about to take possession of a 2.5 story double brick house with a finished attic in Ontario. Like most of the houses built at the same time, the house has little to no insulation. Consequently the attic (12' x 24' with a slanted 8' ceiling) is stifling hot in the summer, and much hotter than necessary in the winter.

I am planning to install A/C in the forced air heating system. However I'm wondering if there isn't a better way to normalize the temperatures in this room. Would any of the following work:

1) Install a ventilating fan that runs continuously to exhaust the ceiling of the attic to the outside. (This would probably increase heating costs in the winter though). I plan on putting a bathroom in the attic so it could be combined with the bathroom fan or it could be separate.

2) Install a jump duct between the attic ceiling and the 2nd floor hallway space (where there's a furnace inlet duct)

3) Same as option 2, but use a powered fan.

Any thoughts? Be creative!

(BTW, apologies if this is a double post. I tried to put this up Thursday night, but I don't see it on the board)

 

[EnergyProfessional]

your fan only works if the outside air is colder than what you need. Otherwise you just draw in more warm air.

you might want to have a separate AC (window unit etc.) for the attic since it's cooling needs will be so different than the rest of the house. I assume that has AC.

Is it one single forced air system now, meaning one furnace serving both attic and rest of house?

 

[NuclearNerd]

There would only be one central AC (attached to the furnace) in the current plan. The thinking is that option 3 would help equalize the temperatures between the attic and the first / second floor, making the whole system more efficient.

 

[KiwiMace]

You should seriously consider blowing insulation as a first step.

Your other options add a lot of load to an existing system, which will probably make the whole house warm in summer. Add more ac.

 

[NuclearNerd]

I do mean to look at reinsulating the attic bedroom.

I'm not sure how adding a return duct/fan in the top bedroom to pump hot air to the bottom of the house (where it will start floating up again) will increase the load on the system. Shouldn't it just help balance the temperatures?

 

[ChrisConley]

The 'easiest' way to normalize temperatures in the house is to run the furnace 24h/day.

 

[macmet]

Is there something you can do with the outer roof surface that may reduce the amount of heat absorbed? Reflective or solar panels perhaps?

Plus, re-insulate the ceiling. If that's too expensive, maybe you only have to do one side of the ceiling at a time. I lived in a similar house in Ontario, and it faced North. The upper floor was always hot in the summer, but the room with a south facing roof/ceiling was always considerably hotter than the room with the north facing roof/ceiling.

And it will add a load to your AC if you just balace the heat. Think of it as you injecting heat to the 1/2 floors that your AC will now have to compensate for.