We have an inspector taking his job more serious than alot of other inspecters and u bash him =/.... he was asking for an answer to a legitimate question. dont get me wrong i think most inspecters are screwballs. but u cant knock him for asking,he's attempting to do more than most.last time i checked this was a useful site for learning
Thanks for the replies. However, there seems to be some minor disagreement in the group ...
Steve Wiggins said: Yes that is proper and thanks for the pic. Some cities want to see mastic on the vapor barrier but I wouldn't ever recommend that.
davidr said: Peter a lot of times that type of duct design has so much pressure drop over the various fittings it just can not properly deliver airflow. We have gone in on jobs before & renovated duct systems where we had to remove this type of design.
tin_fab said: That method is called the "static regain method" and I can tell you from experience that it is still used by people that want value rather than price (many still around, you just have to sell TO them). I only use rectangular, wrapped.
It seems that although "proper", this design may not be the best alternative. Since the builder is likely to use the same materials, can anyone offer a solution to provide better airflow to the various trunks?
I'm way out of my element here, but I promised my customer that I would do my best to help. FYI, this is part of a pre-sheetrock inspection ... normally I would refer the client to a pro, but in this case, I have to provide convincing evidence that the builder's HVAC installer could have done a better job.
I am a professional real-estate inspector. I own my own company (visit my web site if you like). I am not a building inspector. I do many different kinds of inspections ... all the way from slab to finished product, and I am experienced and educated in many different aspects of residential and commericial construction. I am a "general practitioner" ... you are a "specialist". I know a few things about many subjects, whereas you know many things about a few subjects. I accept your apology, and I apologize for that "last laugh" jab.
I have a report to write ... What should I say about this duct design? Here's a first cut:
"The HVAC ductwork in the photo, although branched correctly, may not provide adequate airflow to the smaller diameter sections of the branches. Recommend a qualified HVAC professional evaluate and determine a course of corrective action."
I would like to be more specific about a remedy that uses the same materials. However, I do not wish to "pi** off" the builder's pro.
important clarification: tin fab's reference to "static regain method" was referring to my reference to a "graduated ductwork system" utilizing all rectangular fittings. Please don't confuse the system we are referring to with what is shown in this picture. We are talking about two entirely different systems. Correct me if I am wrong tin fab.
>>I have a report to write ... What should I say about this duct design? Here's a first cut:
>>"The HVAC ductwork in the photo, although branched correctly, may not provide adequate
>>airflow to the smaller diameter
>>sections of the branches. Recommend a qualified HVAC professional evaluate and
>>determine a course of corrective action."
>>I would like to be more specific about a remedy that uses the same materials.
>>However, I do not wish to "pi** off" the builder's pro.
Like you I am in S.Texas, we are almost close enough to be neighbors. One of my good friends lives in Round Rock. I am a homeowner who tries to educate himself, perhaps you will forgive me for asking an ignorant question.
PJSullivan, I do appreciate an inspector who learns more than the minimum, and want buyers in general to be well protected against defects. But there is such a thing as raising false warning, and that is a holy PITA to the seller. During a recent home sale I had the unpleasant experience of an inspector raising false warnings. I want to ask you, what exactly is the basis for raising this as a homeowner problem?
I submit that the actual method of duct construction is not sufficient to say it "may" not provide adequate airflow. Of course if one of the duct experts such as Dash will give a contrary opinion, I will gladly defer to his judgement.
Requesting a Manual D analysis of the duct system would give professional evidence of its adequacy or inadequacy, but is that the norm anywhere in home inspections? Directly measuring supply airflow with a flow hood would also be professional evidence. But such a thing is so out of the ordinary that I have to wonder if it is really within the professional norms of the inspector.
It seems to me you have an equal basis for alleging any other deficiency of the HVAC system. How do you know the system is sized to the house's cooling or heat load? How do you know the airspeed is under the 700 fpm limit stressed by Manual D for flex duct? In each case the homeowner would benefit from having the system tested (except for cost of testing), but what is the basis for raising the original accusation? I submit that there is not enough basis.
My skepticism is colored by the fact my own attic ductwork resembles the picture you showed. I am not under any illusion that my house has great ductwork, but after several HVAC guys have looked it over, they have found various things to criticize but I don't remember any raising the objection you have. I have actually had measurements of supply duct flow made, and they are reasonable. After addition of some much needed return ducting, ESP for the system is in the range of .45-.60 inches of water column depending on filter loading, about .35 if the furnace is on low speed. Not ideal but with a variable speed fan not a source of big problems either. It seems if the construction method were going to cause pressure drop and airflow problems, the measured ESP would be higher and/or airflow would be lower.
Just a devils advocate thought. I am sincerely interested in learning what is right.
Best wishes -- P.Student
[Edited by perpetual_student on 01-08-2005 at 10:27 PM]
First of all, I appreciate Mr. Wiggins for reminding me of TREC's standards of practice about what I am not required to do. Just because I am not required to do a thing does not mean that I am not free to do a thing; provided of course that I am well grounded in what I write. I know inspectors who often learn about a subject thoroughly, and offer opinions based on their well researched knowledge; however, they (and I) never imply that we are a professional. In fact, I always defer to the professional in my reports.
I'm simply trying to determine if something is installed correctly. The customer raised the issue, not I. He wanted me to research the subject, and see what I could find out.
As I'm sure you are all aware, homes in this part of the country are literally thrown together by immigrant workers who cannot even speak English. In fact, in my county, if you want a job as a building superintendent, you have to know how to speak Spanish (a sad situation). So, as a result, many homebuyers harbor a deep mistrust for builders because the customer rarely gets what they want because of miscommunication, etc. So, when the customer saw this (he's an engineer), he asked what I thought. I said "I don't know". He asked if I could find out if it's ok. I said "I would try". Hence, my question. I'm not trying to be a HVAC pro. That's why I came here. Isn't this forum for people who want answers to HVAC questions?
How about this ... forget the fact that I'm a home inspector. Pretend that this is my home. I have this ductwork. I'm concerned that the airflow may be inadequate. I have come here requesting a professional opinion about whether there is a concern or not. So far, I have received many different replies ... some say it's ok ... some say it's not. I've already spent way more time on this than I wanted to. Can anyone help me, or should I go somewhere else?
If you really want to learn what makes good duct design, you can buy the ACCA Manual D book for about $40. I did, it's not an easy read but the info is in there. What I expect you will find is that sizing is more important than type of construction. And I will say again that size needs to be measured against the job the HVAC system needs to do, how can you criticize the duct system without equally examining the AC system, and how can you criticize that with no knowledge of the heat load on the house? Lotta questions that are easier to ask than to answer.