rafter spacing and skylights

[oldnewhouse]

Hi all,
I'm getting toward the end of making our upstairs livable. I'm in a 100 year old bungalow where the previous owners did a craptacular job of finishing the attic. I have rafters that are anywhere from 18.25 to 18.75 inches apart. We need a venting skylight to imrpove circulation and make it more livable. Most of the offerings require a 21" or 30" hole. I don't really want to cut a rafter, but it looks like the only option. What would you do? what is the strongest way to make this repair? should I look at other options? I know they make 14" skylights, but they are all kinds of expensive and really too small for the application we want.

thanks
Mark

[Wgoodrich]

My opinion your skylight will let in as much heat from the sun and roof surface as the air flow would be produced to eleviate heat concern. If it were me I would skip an opening skylight and worry more about insulating that roof properly and allowing air flow between that insulation and the underside of the roof decking. Then I would invest in windor air conditioning to vent and condition the excess heat and stale air in the finished attic. Did you check to make sure your ceiling joists for this finished attic made to be floor joists were rated to carry the load and did you beaf them up where requried?

Just some thoughts

Wg

[oldnewhouse]

our rafters are 2x4's. there is no room for more insulation or additional space. Also, code here requires cross ventalation, that can't be obtained with windows becahse the roof has a gable on one end and a hip on the other. If we don't add ventalation the window AC won't work, and the space won't be able to be counted as livable space when we sell. There is no room to lower the ceiling - doing that will make it feel like a cave.

[Under_Miner]

Typically doubling or even tripling up the rafters on either side of cut trusses can take stress off the cut truss (these are called trimmer rafters), also ensure that you place doubled-up 2x4 "Headers" at the top and bottom of your opening and use hangers at the headers where you cut the rafter for the opening.