Insulating the roof exit hatch
 

Our house doesn't have an attic, there is just a 50cm thick slab of concrete on top of the last floor. In that slab is a "tunnel" with a hatch at the top, allowing access onto the roof.

http://ecorenovator.org/forum/attach...9&d=1253803176

In the above pictures the two arrows show where you can see light from the outside. This means that the hatch doesn't insulate very well (you can feel cold air dropping down onto you when you stand under it in the winter). So, the first step was to add an insulating liner around the frame of the hatch to seal it.

The next step was to add a second hatch under the first one, creating a 15cm airspace between them, something like a double-pane window. The inner hatch is just an old board I found in the garage, cut to barely fit in the tunnel. I glued two pieces of 5cm thick scrap styrofoam to the top side for extra insulation, and added a handle on the bottom to ease removal.

http://ecorenovator.org/forum/attach...0&d=1253803176

The new hatch is pressed to the bottom of the frame with a wingnut in each corner. The perimeter of the frame bottom will also be lined with an insulating strip so that the joint with new hatch is also as airtight as possible.

http://ecorenovator.org/forum/attach...1&d=1253803176

This will definately reduce the amount of warm air the house loses through the hatch in the winter, though I doubt that it is enough to put a noticeable dent in the gas bill. Hopefully it will be warmer upstairs.

Nice job Piwoslaw.

Is that light I see coming through the door in the first picture? If it is, did you seal that up?

Update
 

I added insulation around the perimeter of the frame, both on the top side and the bottom. From the bottom, the new hatch presses against the insulation when I tighten the screws. The old hatch closes onto the top side and lays on the insulation, but the frame is so uneven that there are still finger-width gaps in a few places, but it's still much better than before:)

If we decide to add insulation to the whole roof within the next 2-3 years, then the external hatch will have to be raised, so then it can be made airtight and insulated.

For now I have to move on to the next draft-reducing project: Partially closing the ventilation shafts that connect the rooms with the chimneys. We're losing lots of heat through them in the winter.

I was just thinking... Why do you need the hatch? Any possibility of just filling it in completely?

Unfortunately, the only other way to get on the roof would be an 8 meter ladder - not very stable. Maybe in the future it would be possible to attach a ladder to the outside wall, but not any time soon. We still get up on the roof at least 2-3 times a year (pre- and postwinter maintenance, plus realigning antenas), so the new hatch increases the pain-in-the-whatever factor, but the savings are still worth it :)

BTW: We had some heavy rain today and it's much quieter upstairs with the extra layer of insulation.

Condensation!!
 

Two days ago we got a mess of snow here, like 10-15cm, it still hasn't melted away. The hatch insulation was doing fine, couldn't feel cold air dropping like usual in this weather.
Unfortunately, this morning there was a puddle of water on the floor under the hatch :( This got me worried, I thought maybe I drilled too deep with the screws? So I unscrew the new internal hatch and I see that the external hatch is dripping wet with condensed water.

http://ecorenovator.org/forum/attach...2&d=1255675981

http://ecorenovator.org/forum/attach...3&d=1255675981

So here is my theory: The old hatch is fiberglass and doesn't insulate well, so we were losing lots of heat through it. That heat would melt any snow laying on it. Add that it wasn't sealed well and there was always lots of airflow around the edges (warm air leaving, cold coming in) which took any vapor with it. Now, with the second insulated hatch in place and more seals around the perimeter, the old hatch is much cooler and there is much less airflow. Since it is in the highest point of the house, warm moist air will naturally rise there and since there's not enough draft to suck it out, will condense on the external hatch.

So, what do I do now? If I put the new hatch on the problem will persist. If I don't I'll keep losing heat, eh. Next year we plan on redoing our ventilation into an active system that will suck warm air from the kitchen and bathrooms and run it through a heatpump to warm water. I could add a small duct to suck air from around the hatch, since it's the highest place in the house. If we have enough $$$ I'd also like to add insulation to the roof, and then I'd replace the old hatch with an insulated model. But until next year it looks like I'll be losing heat :verysad:

I haven't given up!!

Here are more pictures of the hatch. Notice how thin it is. It is a wooden board, covered with fiberglass on the inside and a sheet of metal on the outside, so it's only about 4-5cm thick.

http://ecorenovator.org/forum/attach...1&d=1289307489

http://ecorenovator.org/forum/attach...1&d=1289307489

I decided that the best way to insulate the hatch would from the outside. I contacted a roofer because he would do at least twice as good as I would. He added 10cm od dense styrofoam on the outside, put metal around the perimeter, and stuck an asphalt shingle on top to waterproof it. Much better than I'd do.

http://ecorenovator.org/forum/attach...1&d=1289307914

http://ecorenovator.org/forum/attach...1&d=1289307489

Other than being much thicker, it's also heavier, making a better connection with the seals. If this new insulation will totally stop condensation, then maybe a could still use the inside hatch I made last year to reduce heat loss even more.

Looks much better.