Insulation in flat, low attic


Old 10-06-04, 07:52 AM
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Question Insulation in flat, low attic

My attic leaks heat like crazy. From what I've read I want to blow cellulose insulation into my attic, over the existing, settled insulation, to improve the R value up there. It also sounds like I need to allow for ventilation and not block vents, etc.

I live in a townhouse complex and my north/south walls are shared with my neighbours. I haven't been on my roof and don't know if I have access to my attic from there but I doubt it. I don't have any inset light fixtures to worry about - a washroom fan is about it. All the attic's ventilation seems to be through the roof. I heat through electric baseboards (ouch!) so I have no duct work.

My problem is that the attic space is about a foot high. I can't crawl around in there with the hose or after insulating to ensure everything is spread evenly and that I still have a good ventilation space. I have been given advice that I would need to drill a hose-sized hole every 7 or so feet and blow the insulation in that manner. No one seems to know what to do to ensure the insulation is evenly distributed and that ventilation can occur.

Any suggestions?
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Old 10-13-04, 06:01 AM
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Unhappy Stumped

Did I stump the panel with my posted question? No one else can give me an answer so it doesn't surprise me too much.

Thanks anyway.
Old 10-14-04, 09:29 AM
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Location: USA
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Professional insulating contractors will gain access to the attic space to assure desired coverage. In most cases they will go through the ceiling and not drill holes every 7 feet. If there is access through the roof then they will use that. Adequate free venting only occurs with moderate sloped roofs. In other words, the high and low vents must be separated by a minimum of three feet in height. So the only acceptable practice with low sloped or flat roofs is to have a minimum of two vents that are on opposite sides of the attic space on the high side. On the low side of the attic space, the insulation is usually applied between the ceiling to the roof decking. This is usually done for only a third of the attic.

In the early 1980's I was involved in the "Attic Insulation Program" (AIP) in my State. One section of the program involved 1,500 row house throughout my State major cities. It just so happened that the average age of these row houses were 75 and they all had flat roofs. State and/or Federally funded programs like these become case studies. They come about by proposed Societal, Economic, Environmental and Occupant Impact reports. I was involved in the data collection where I physically inspected the dwellings, interviewed the occupants and analyzed each fuel history for over a 10 year period. Of course the inspections involved more than just the attics, in fact it involved everything, heating systems, electrical, plumbing, fixed appliances and the rest of the structure. Everything was rated and recorded. I was told by my wife towards the end of the program that my site visits exceeded 10,000. I don't know because I was too busy doing inspections and paperwork so she did the books. To give you an idea on how large this program was, I was one of 44 inspectors/auditors.

HUD was so impressed with these statistics that they decided in the mid 1980's that they looked for a major city where the average house was over 60 years old and the vast majority heated their homes with oil and had no attic insulation. HUD used these statistics to convince the Department of Energy to fund the program. It claimed that insulating every attic in this city, it would reduce the heating oil consumption by a third. That city was Bayonne, New Jersey and it took a year to insulate.

Even though I did not agree with the method of insulating attic for low/flat roof structures because of the ventilation issues, out of all the inspections I did and meetings I attended, which included discussions on those concerns, there were no indicators that the method caused structural problems. I will admit there were several attic structural failures identified by me over that period of time. However, there were contributing factors to the failure that had nothing to do with either insulation and/or ventilation. The housing stock was usually built around the turn of the century. Maintenace was usually a major contributing factor. Fires took place in a lot of these structures and the repairs were improperly or not done at all. It was not unusual to find charred rafters. Using a pot to catch water pouring through your ceiling does not solve a roof leak and the resulting structural damage by not repairing the roof properly. Multiple layers of roofs is also very common cause of the structural failures. The substrates (roof decking) failed in most cases from leaks. So much so that if you stood over the affected area, you would fall through the roof. Their solution found in most cases were to add a layer of plywood over the old roof and roof over that.

Even though I am a strong supporter of adequate attic ventilation, I am also practical. In a situation like yours, I would recommend insulating as first mentioned in this reply. I can take a guess why ventilation did not become an issue with this type of structure. It is probably because low/flat roofs are water proofing systems whereas, steep roofing systems are water shedding systems. I will admit, I do not have any information to support that guess.
Old 10-29-04, 10:58 AM
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Thanks for the info resercon.

My neighbour and I got a reputable professional to look at it. There is actually only 8 inches of attic to work with. He said if we added anymore insulation we'd cause condensation to occur and we'd have rot in a matter of years. We would have hired him to do the work so I'm fairly confident in his assessment.

Looks like the only option is to drop our interior ceiling 6 inches or so and put more insulation in that way. Too bad. That's a much bigger job than I was hoping for.

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