Friday, January 15, 2010

Jan 15 inspection number7

This certainly shaping up to be a typical January. That being painfully slow, and if next month stays true to form it should be even slower. I am usually pretty happy if I can get 18 inspections in January and the same in February. It is all just part of the business, if you choose to live and work in the rural settings this is what you have to get use to.
The last two inspections, on Wednesday were both pretty none eventful. Which, from a buyer, seller, and agent stand point is, as I said before just what every one wants.
This is not to say that both of these homes were with out concern. It is just that both the concerns, when convey in a non alarmist fashion and therefore were deemed( rightfully so) as being manageable, in this case, as well as typicall. In fact the two biggest concerns in these house were the same. There is some irony in this due to the fact that there is about a 50 year difference in age. The concern that they were both dealing with is a problem that easily 75% of the housing in Ontario deals with. The scourge of this winter wonderland we call Ontario, The nemesis of new and old housing alike, regardless of social status, the rich or poor. The plague we know as the ICE DAM. ( pretty big intro for something that can be easily summed up as a simple pain in the ass { and pocketbook})
However you want to define it, Ice Damming is a problem that we ( in the construction industry) have been aware of for a very long time. While we are aware of it the fact still remains that it is (can be) a tricky problem to effectively, and completely address. Let me give you my two cents worth.
Cause: 1. Interior heat loss to the attic space (most of the time)
2. Lack of ventilation in the attic space ( some of the time)
3. Air leakage into the attic (often)
4. Additions (occasionally)
5 Exterior, solar thermal loading ( rarely)
Now here is the kicker, all of these concerns can be compounded with the introduction of intricate roof lines.
The explanation of each of the five bullet points are as follow.
1. This is usually the first culprit to address but unfortunately it is not always as easy as just dumping some more insulation into the attic. In the first older house, of the two inspections that I did on Tuesday the insulation medium that was being used was hard wood chips. While this may seem odd it is a common occurrence to find this type of material being used as an insulator. Remember that more often than not older homes were made by the owner, and not that long ago. My dad with assistance build his first house in the fifties. Now he had enough money to use proper building materials but many did not. It is common to see used materials in old homes, The home we are speaking of had logs, old barn beams, and standard 2x8 lumber making up the floor joist. ( Recycleing has been around alot longer than you think) Ok I am off on a little bit of a tangent, lets get this ice damming talk back on track. While this home was certainly in need of the attic to be re-insulated I was not convinced that this was going to be the total correction. In fact I felt that the problem was much a little more difficult to address. The frost pattern on the underside to the roof sheathng ( observed form the attic space), which was most intense a top of the walls, was I believed in all likelyhood,due to the wall insulation being equally as poor.
Understanding the basics of ice damming is an important start. During the winter months we develope a blanket of snow overtop of the roof . As we have warm air escaping our building envelope and entering the attic the warm air rises to the underside of the roof where is sits. In doing this it warms the underside of the roof sheathing enough to cause about an eigth of an inch of snow to melt which in turn runs down the roof, all the while the snow blanket above it insulates the melt water from the outside air, ( go figure) once the melt water passes over the roof overhang or the soffit where there is no longer any heat the melt water freezes. This is where the perverbial dam begins. As the melt water continues to run down the roof the dam builds larger and larger untill the water can no longer go over top. Now the leaks begin, the water finds its way under the shingles and leaks into our homes. In the case of the home I inspected the bulk of the air, I suspect is rising up through the wall cavities.
House insulation has a nasty habit of settling, or compressing with age, yes like you and me your attic insulation sags with age too. Equally every time the plumber, electrician or home owner go into the attic they disturb, move, and compress the insulation and rarely do they put it back or "fluff" it up, and now we have more potential air leakage. There are a lot of different types of inulation that have been used over the years some good and some not so much. All of which have varing capabilities of resisting the passage of heat / air through them. This is a whole other subject that we surely will discuss another day.
The second on our hit list is ventilation. I have, what I suspect is a different take on the venting of roof attic spaces. I will pass it along to you as food for thought, it is something that needs to be re hashed over I feel. The Ontario Building Code (OBC ) states that we should have not less than 1 sq. ft. of roof venting for every 300 sq.ft. of insulated ceiling. Heres where is gets a little complicated. Not less than 25% of that ratio has to be in the roof line and not less than 25% of that ratio has to be in the soffit. Wait....... we are not done yet. If the roof pitch is less than 4 in 12 ( going off memory here) than the ratio is 1:150 meaning about twice as many vents. Now if that sounds like greek to you let me try to give you some prospective on that. Every one of those little square vents that you see on a roof equates to just slighly over a half of one square foot of venting. While these are commonly put on only one side of the roof the correct applicaiton would see them equally placed on both sides of the roof. That being said if we were going to live by the letter of the law then a 1500 sq. ft. home with a straight gable roof (triangle shape) would have approximately 6 to 8 vents placed 3 or 4 on each side of the slope of the roof about 16inches below the ridge line ( peak of the roof) and a completly perferated soffit with insulation baffels placed on the inside to ensur that the insulation does not plug the soffit vents. Heres the part that bugs me. This deals with the results of the problem. Would it not make more sense to deal with the cause of the problem . AIR LEAKAGE. I'll let you chew on that for a while.( As a sub note a continuous ridge vent is by far a better venting system) This brings us to number 3 on our list
Every time we put a penetration through our ceiling it is a potential spot for air leakage ( how many pot lights do you have?). What does your attic access look like? How many chimneys do you have in your house? Not real chimneys as we know them I mean holes in the ceiling. Everyone of these penetrations are acting just like a chimney for heated air. Yes I am sure you have a vapour barrier ( depending on age of the house) under your drywall but I am also sure you have 15,736 holes in it This due to everything from drywall screws, staples, light and fan fixtures and of course the big daddy of them all the attic access. End result, lets do the math. Penetrations + air leakage = ice dams.
Number 4 on the list is a tough one. It likely is more of a contributing fator than it is a cause. It is common to find areas that have been worked on during additions and have not had enough detail paid to the seams of the addition to the existing building. An old place that I use to live in is a perfect case in point where an addition was put on but due to the fact that not enough attention was paid to doing an effective job at insulating the seams where the two met I had air leakage and because the new roof line was built over the old one there is now a spot for the heat loss to be trapped becuase the venilation that is suppose to be dealing with the results of the problem is also now very restrictive.
The 5th is a little more rare to see but when this is the problem it is very difficult to deal with. So your choices are move the sun or move the building, good luck with that.
It is a case that the winters sun being low in the horizon will cause the roofing materials (usually metal) at the top of the roof ( steep pitchs are most suseptable) to warm up to the point where the some snow melt begins to occur. The sun is in most cases not out or warm enough in Febuary to completly melt the snow off so the melt water runs down the roof only a few feet and then re-freezes where the roof is shadded and creates an ice dam. Not at the eaves but half way up the roof, In this case I have seen not only where the water backs up and leaks into roof vents but where the ice will slide down and tear roof vent off .
Ice damming ? In my mind still a big question. If you were to ask me, I would say that my understanding level of the problem is about 60%. I say that because about 40% of the time I am left scratching my head as to what is causing it this time. Be leery of the guy that tells you he has it 100% figured out , he just has not seen enough of them yet.

It's been fun talk to you later

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