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Double wide rebuild

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Double wide rebuild

Postby » Fri Nov 28, 2008 12:18 am

Hello there:

I am about to put a bid in for a 2001 double wide that has been unoccupied due to mold issues and kind of neglected since 2006. I may get it for a good price, however a lot of rebuilding needs to get done and I want to increase heating efficiency quite a bit. In my ideal, romantic world I want to heat this home with a (large) candle. According to the manufacturer the walls are R19 and the roof is R30. I would like to construct another 2x4 interior wall with staggered studs and insulate that to get better (and more sound-proof) walls. A new vapor barrier would seal out any mold that may still linger in the existing walls. They did some work to get rid of the mold but are covering their rears with statements like "the entire extend of the issue is not known".

Anyhow, my biggest headache is the roof. There is no point in adding insulation to the walls if the roof cannot be insulated more as well. What is on the roof right now is a low pitch truss (I assume it is a truss) with glued on sheetrock panels, sprayed on vapor barrier (I assume) and blown in mineral wool. Asphalt shingles on top. I was told there are 2x4 rafters, 16" apart. I am assuming there is some sort of truss structure underneath otherwise there would not be enough room to blow in enough mineral wool to achieve R30.

What is the best thing to do to get R50 plus more (~12") roof overhang, and maybe more pitch?

Can I strip the roof, add a lightweight wood structure on top, insulate that and use a ventilated metal roof? I feel I need to eliminate the air space between new insulation and old insulation. Should I just blow in more to fill it up? How about insulated metal panels? I do not like that they are not ventilated. And expensive I hear. And not eco-friendly during manufacturing. How about engineered new trusses on top of the old? Too heavy?

Questions, questions....

Thanks.
Karsten
Karsten offline
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Re: Double wide rebuild

Postby » Fri Nov 28, 2008 5:17 am

Actuelly R-19 walls which requires 2x6 studs and R-30 roof is usually considered OUTSTANDING insulation..Most home owners would have to pay contractors a ton of money to get there..You should be mostly concerned with the moisture problem causing the mold...It would be a shame to do all this work and mold make it all a waste..Ask as many questions here you want. There are others here who have lots of renovation and have hands on experience with this type of job..Good Luck
rmurray offline
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Re: Double wide rebuild

Postby » Fri Nov 28, 2008 11:11 am

In these days of mold phobia, this home may not be worth what you pay for it, let alone what you are considering spending on improvements. Once a mold problem is documented, buyers are few and far between and so are lenders. That said, at the level of insulation you already have, you may be able to achieve your goal for less cost. I would suggest removing the siding and wrapping the house with styrofoam and a wind wrap. Reseal and caulk all ductwork, windows and doors as well as plumbing holes in the floor. Like Rmurray said, find where the moisture came from and deal with that first. That is critical.
trmimo offline
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Re: Double wide rebuild

Postby » Fri Nov 28, 2008 2:16 pm

Well, I am glad that this is considered outstanding but, I am afraid, it won't be considered outstanding much longer. Even 30 years ago such insulation values would have been considered below reasonable by those who cared about the heat loss. In the 70s, R40 walls and R60 ceilings were deemed great by architects that dealt with energy conservation. Today some people want up to R100 in the roofs and some of the buildings they create can be heated almost entirely with the body heat of the people living there. It makes little financial sense when energy is inexpensive, but it sure looks like cheap energy is going away and I want to be ready. What is the point of your house wasting tons more energy than you ever save with installing energy efficient light bulbs or recycling every scrap of plastic. In a way, I would also like to demonstrate that it is possible and makes sense to increase insulation.

However, you are very right that the mold and the moisture problem have to be addressed first. It sounds like that there was a problem with the washing machine and the person I talked with said it originated from there. I will find out by opening a few more wall cavities and looking under the floors where water could cause trouble. At lot is already opened up. Air-tight homes are good, but not if ventilation is inadequate or vapor barriers are installed incorrectly.

Yes, the current exterior walls are 2x6. The wall I mentioned building is an ADDITONAL insulated wall that goes on the inside of the building. It almost doubles the exterior wall.

Any thoughts regarding my ideas for roof re-design?

Thanks.
Karsten
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Re: Double wide rebuild

Postby » Fri Nov 28, 2008 10:54 pm

30 years ago R 11 was considered good... the price of oil was so low that was all that was required in most residential structures. The insulation that is already in that home is considered very good by today's standards... that should not preclude you from adding more. You do reach a point of diminishing returns and as you seem to understand you can get too air-tight... ventilation is an important key

Regardless of the insulation issues you nee to be sure that the mold is 100% gone before you invest in any additional improvements. You can not just burry the mold under new walls. As long as there is live mold it will continue to grow and become more and more of a problem and health threat as time goes on.

Mold is a potential problem in any structure and needs to be avoided or removed when it occurs.

"Molds are part of the natural environment. Outdoors, molds play a part in nature by breaking down dead organic matter such as fallen leaves and dead trees, but indoors, mold growth should be avoided. Molds reproduce by means of tiny spores; the spores are invisible to the naked eye and float through outdoor and indoor air. Mold may begin growing indoors when mold spores land on surfaces that are wet. There are many types of mold, and none of them will grow without water or moisture....

Molds have the potential to cause health problems. Molds produce allergens (substances that can cause allergic reactions), irritants, and in some cases, potentially toxic substances (mycotoxins)."


Read more from the U.S. Environmental Protection Agency

  • Mold Basics
    • Why is mold growing in my home?
    • Can mold cause health problems?
    • How do I get rid of mold?
  • Mold Cleanup
    • Who should do the cleanup?
  • Mold Cleanup Guidelines
  • What to Wear When Cleaning Moldy Areas
    • How Do I Know When the Remediation or Cleanup is Finished?
  • Moisture and Mold Prevention and Control Tips
    • Actions that will help to reduce humidity
    • Actions that will help prevent condensation
    • Testing or sampling for mold
  • Hidden Mold
    • Cleanup and Biocides
  • Additional Resources





  • As far as the roof.... You really dont want to start redesigning the roof truss system unless you have extensive engineering experience. Changing the size or shape of the trusses will change the stress loading which could require other structural changes down to the foundation. I'm getting ready to add insulation to my roof. I'm going to install a 50 year designer metal roof. Instead of installing the new roofing directly over the old shingles we will frame the edges with 2x4s and put 3 inches of Styrofoam between the old roof top and the new metal pans. If you have not done this before there are pre-designed systems that can be easily installed. Take a look at the example at http://www.structall.com/content/pdfs/RoofOverGuide.pdf

    You can also just add insulation to the existing roof see the 3 VIDEOS we have online "Adding Insulation to Your Manufactured Home" for two methods used by the U.S. Department of Energy's Weatherization Assistance Program (WAP) for installing additional insulation in a manufactured home roof. You can find that at http://mfdhousing.com/portal/stories.php3?nid=5604
    David Oxhandler
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    Re: Double wide rebuild

    Postby » Fri Nov 28, 2008 10:58 pm

    So, from the outside? I have (if I get the home) very little roof overhang so I will not be able to add more than 2"to the exterior. Which brings me back to the roof. How do I change that and add overhang (with which I could consider adding the insulation under the siding as you suggested).

    If I get the place for the price I will bid, I won't be paying for the building. Just for the land, water, septic, electricity, and the slab. We will see. I still have not decided how to proceed regarding the renovation. I am not finding the answers I am looking for regarding the roof. Sorry for being so obsessed with the roof roof.

    Thanks,
    Karsten
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    Re: Double wide rebuild

    Postby » Sat Nov 29, 2008 2:14 am

    Eves (overhang) can be added to any roof by framing an addition on to the edge of the roof. keep in mind that when you continue the pitch of the roof out, you may overshadow the tops of your windows, or affect other trim components on the upper sides of your home ... If you do extend the roof with out major tie ins to the existing truss-rafter system you need to be very careful getting on the roof in the future as the edges will be unsupported. So make sure you do some serious planning prior to starting. This is a huge job. There are allot of factors and variables that can only be addressed with a site visit. If you have not had much roofing experience this is not something to try solo...

    With some of the metal roof systems you can extend the metal over the edge. I have done this by as much six to eight inches which was enough to get rain water off the exterior walls. Again in that situation you have an unsupported edge which must be considered every time someone gets on the roof.

    Prior to doing anything you should find out what the local construction standards are from your county or town building permit office. Most of the type work your thinking about requires a licensed contractor, permitting and inspections in most counties You dont want to invest in renovations that the local building authorities might condemn the day you finish. Get a few experience roofers to come to the home and get thier thoughts and take bids for the work.
    David Oxhandler
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    Re: Double wide rebuild

    Postby » Sat Nov 29, 2008 3:53 pm

    Thank you David, some very good point to consider. I looked at the videos and thought this is something I can do. I did check out all the info about mold you posted. I have a little daughter and her mother will bite my head off if I expose her to a house that is not mold-low (since completely getting rid of it is impossible). I will have the home tested when I think I am done with the mold removal.

    There is one point I do not understand about roof insulation though: Why put insulated roof panels (or foam panels) OVER an insulated roof with an airspace BETWEEN? Does the fresh air circulating there not defeat the purpose of the added insulation? Should you not first eliminate the airflow of the existing roof and then add more insulation with ventilation above that? If you don't do that you lose heat to the already existing airspace and the air carries it away. The added insulation is not efficient. We make the insides of our homes draft free well knowing that air infiltration is the major factor in heat loss. But we do not consider this when building our roofs? It is like wearing a thick jacket that lets the wind whip through. You feel that. I know - I have one like this and it only works well if the wind stays out.

    What do you think about self-supporting roof-overs? Those that carry the weight of the roof with the help of 4x4s that sit on the foundation. Maybe a 2x4 roof structure, foam panels in between, strapping and metal roof, AFTER removal of all old shingles to shed some weight?

    Thanks.
    Karsten
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    Re: Double wide rebuild

    Postby » Sat Nov 29, 2008 6:27 pm

    A self supporting roof is a very expensive alternative. Price out some of these ideas to see if your budget can stand the shock.

    "Attic ventilation is an important part of roofing. Proper attic ventilation extends the life of a roof and reduces problems because it minimizes the temperature differential between the attic and the air outside. Proper ventilation will remove moisture and heat from the attic. Trapped heat and moisture can raise energy costs, cause ice dams, and damage roof system components as well as structural and personal items located inside the attic where temperatures can easily reach 150° F (65° C). Condensation that forms inside attics can be caused by the use of washing machines, dish washers, bath tubs, showers, and tumble driers unless these items are properly ventilated through the roof. In some cases the condensation can be bad enough to be mistaken for a roof leak.

    Here are some problems associated with an improperly ventilated attic space.
    Sumps between rafters (deck deflection) can happen because after awhile (sometimes several years, sometimes only a couple years), a plywood roof deck can warp or deteriorate and become spongy and dangerous to walk on. This occurs because one side of plywood decking needs be able to "breathe" by being exposed to circulating air. The adhesives used in the plywood can deteriorate or Dry Rot can occur because of condensation.

    Water vapor will condense first on anything metal inside the attic; this will eventually cause the metal to rust. Heads can rust off nails, metal plumbing straps or straps holding HVAC ducting can rust in two causing the ducting to crash down on top of the ceiling joists or through a suspended ceiling. This problem is more common in humid climates.

    In colder climates – generally where the average January temperature is 32° F (0° C) or colder – high inside humidity (40% or greater) combined with low outside temperatures can cause frost to form on the bottom of the roof deck.

    Insulation can trap moisture which will reduce the R-value of the insulation and create a nice environment for the propagation of certain molds, spores, and fungi which will also cause problems.

    There is also the problem of mildew which is both damaging and can cause health problems.

    The roof system itself will deteriorate prematurely.
    Cooling units will need to be serviced or replaced prematurely because of excessive use.

    Ice Dams - ice dams are the result of melting snow continually refreezing at the roof perimeter and then backing up under the shingles and causing leaks. Proper ventilation used in conjunction with heavy insulation and an air barrier can create a Cold Roof Assembly which will help eliminate ice dams."

    Source: http://www.roofhelp.com/ventilation_main.htm
    David Oxhandler
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    Re: Double wide rebuild

    Postby » Sat Nov 29, 2008 10:16 pm

    I understand that the biggest problem of moisture in the roof is that it gets there in the first place. That's how a good vapor barrier will eliminate this problem. Also, I read a quite interesting study about attic designs and some even talk about eliminating ventilation since it is not proven to do any good in some cases (unless you have humidity traveling into the attic). I did not read it all very well though. http://www.mhrahome.org/media/reports/attic_vent.pdf

    In any case, I believe in ventilating a roof. And I can see how the foam panels over the airspace can help eliminate heat entering the building. I cannot see how they can help against heat loss though. Or at least not as well. But the fact that plywood or OSB needs to breathe at least on one side supports keeping an airspace under the deck.

    Is there reliable, independent data available regarding how much the R-value increases if foam panels are added on top of the deck? It cannot be as much as the material itself due to the airspace.

    Thanks!
    Good advice. Many answers.
    Karsten
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