Problem identifying air leak under enclosed porch


  #1  
Old 12-31-01, 11:43 AM
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Question Problem identifying air leak under enclosed porch

I have an enclosed porch that is very cold and drafty. On windy days the draft is strong. Even though we block the edges of the doorway to the porch, the floor in my living room is cold and drafty. I suspect that the cold air is travelling between the rafters under the floor.

How can I locate this air leak? I tried using a lighted match while in the crawl space under the porch, but I am unable to identify any part where the smoke blows horizontal.

Another thought I have is to fill the crawl space with some kind of smoke like material. My hope is that on a cold windy day, this smoke will be sucked out allowing me to identify the source of the air leak from the exterior. Has anyone ever tried this? Is this advisable? Is there a machine to generate some type of non-toxic smoke?

Any advise on identifying and correcting this air leak will be greatly appreciated.

Thank you.
 
  #2  
Old 01-01-02, 01:33 AM
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Hello: TPERSAUD

The drafty air may not be coming directly, all or in part, only from the space beneath the porch. The space between the rafters is provided to allow ventilation air to avoid mold and mildew, etc. to the sub flooring and structure.

Closing up any air vents etc. may not prove to be a wise choice. However, insulation may be all or part of the answer. Also check for air leaks around windows and doors. Buy and install the self adhesive backing type weatherstripping were and as needed.

Smoke filling a room or space may provide some of the answers for locating air leaks but I have not heard of this method used in recent years.

Some heating agents use non toxic smoke generating devices to check for cracks in furnace fireboxes. You might inquire of them where to buy smoke bombs.

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Old 01-02-02, 12:19 PM
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Tom,
Thank you very much. I did not think of the ventilation requirements.

Do you know of a good book and/or video about detecting and correcting air leaks?

Thank you,
Tom.
 
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Old 01-02-02, 04:46 PM
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Hi: Tom

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Old 01-03-02, 08:48 AM
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Air infiltration is what you're experiencing with your floor. Most people relate to this because of the discomfort associated with the cold drafts. To a building performance specialist, it is an indication of air leakage. To them it represents the source for discomfort and high energy bills. In other words, the same volume of air coming into the home (air infiltration), the same amount of air is leaving the home(air leakage).

I use a blower door and thermal imaging to measure and identify air leakage in homes. The smoke bottle you are referring to is small and very expensive. I only use it for illustration purposes. If you really want to use one, search the web for BLOWER DOOR and look at the accessories that you can order with them. In my opinion, you don't need a blower door or a smoke bottle.

The Utilities contract with people like myself to lower certain customer's energy bills. The Utilities don't want to hear 10 or 20% drop in energy bills. They want dollar amounts per year. Every six months the bills are examined by the Utility and every year for the next ten years, if the reduction is what I said it would be, I get a check. If not, there is a penalty clause.

In every home with a similar situation like yours, I have ever been in, the source of the problem (air leakage) was the wall that has the porch roof attached to it. Warm air leaked through the wall into the roof of the porch causing a vacuum effect in the room, drawing air from the crawl space through the floor. I'm not saying this is the case with you. I am saying in my experience it has been the case every time.
 
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Old 01-03-02, 05:31 PM
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Resercon,
I do suspect that my situation is in line with your experience. Using an incense stick, I am unable to locate any leaks from the windows. Yet, there is a bed of cold air current that seems to come through the floor.

Here is my situation. The porch is two stories. However, the first floor extends further out than the second floor. Meaning that the first floor is covered by the second floor and a small piece of roof on the perimeter.

Last year the second floor was very cold. I noticed some dimples on that little roof that covers the 1st floor. So, I had someone replace the shingles and some rotted underlying wood. In the winter the 2nd level porch was still cold, so I caulked any gaps that I could find on the roof over the 1st floor. I may have affected the roof's ventilation, though.

This year, the second floor is ok, but the 1st floor feels like the outside temperature, with a draft at floor level. The smoke from the incense stick flows upward from every area in the room.

If this suction effect is the problem, what's the best way to identify it and seal it off? Or, should I break the sheet rock and redo with insulation? Should I be concerned about blocking the roof's ventilation?

This problem was starting to frustrate me. I was running out of options. Your advice has encouraged me.

Thank you so much.
Tom.
 
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Old 01-03-02, 07:10 PM
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At the bottom of this message there is a little house icon with www next to it. Click on it and read topics INSULATION, THERMAL BOUNDARY, AIR BOUNDARY and VENTILATION. The reason for this is to give you a better understanding what I'm going to explain to you. More than likely, after you read those topics you'll have more questions. But once you do, you will have knowledge on how things work in the home and apply. After I give you the solution to your problem, you'll be surprised on how easy it was. It's not so easy, if you don't know how things work or apply.
 
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Old 01-26-02, 09:08 PM
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Resercon,
I read the four topics you mentioned. They were quiet beneficial and I do have questions.

Your articles lead me to believe that I have a problem with the air boundary. If so, what is the best way to identify the high pressure areas? Is the floor above the under-porch crawl space considered a "thermal and air boundary area"?

Should I consider replacing the 1st floor roof with a cold roof?

Thank you,
Tom.
 
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Old 01-27-02, 06:09 AM
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Do not replace the floor. The thermal and air boundary is a wall or ceiling that physically separates a conditioned space from a unconditioned space. Therefore the first floor above the crawl space is and the porch floor or ceiling is not. The wall which the porch floors and ceiling attach to is. Since you read the topics, it's going to make it a lot easier for me to explain possible solutions. Thank You for your patience.

Air leakage (high pressure areas) represents your heating dollars loss and discomfort. Also, there are usually telltale signs that indicate air leakage. The damage to the small roof on the first floor porch is one. You don't need fancy equipment to identify air leakage, just knowing what to look for and common sense.

Let's assume the source of the air leakage is the wall (thermal and air boundary) that attaches the porch to the home. The best way to deal with it is insulate the wall. There are two ways you can do it. One is take down the interior walls and insulate and the other is have a contractor blow in insulation. If you do it yourself, pay special attention to the places on the wall that attaches the porch. If you have a contractor do it for you, express your concern about the porch attachments and ask how they intend to address your concerns. You want details on how they intend to address it.

It is true that insulating the floor above the crawl space is part of your thermal and air boundary of the home. However, it represents air infiltration (low pressure areas) and it is advisable to address that area. Doing so will have very little affect if air leakage (high pressure areas) still exists. Another way of putting it is, you control the amount of air infiltration by controlling that amount of air leakage in the home. That is because the volume of air in the home remains constant.
 
 

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