Changing vaulted ceiling to flat to increase efficiency

[Eric_v]

I'm getting ready to buy a 1988 Norris Parkland model 24x60(?) manufactured home for $18k. The home isn't really in need of much work but I want to make it my own so I'm going to gut it and start new. What I'm curious about though is since all the ceilings are vaulted would I save any on my heating / cooling cost by reinsulating and making the ceiling flat to add more space above. I'd also be installing a ridge vent and maybe some large gable vents to allow air to flow through the 'attic'. I will also fur the walls out to 2x6 to allow for R21 insulation instead of R19.

The current homeowner say's they are spending about $300 a month in utility bill and when I went over there she had a/c set at 74 and it felt like 88. I know the a-coil is probably partially to blame due to age and possibly restricting air flow but if I'm going to be gutting it I'd like to do whatever I can to make it as efficient as possible. Is my thought process correct?

Thank you,

EDIT: This is in Illinois

[Greg]

Hi & welcome. I think I would go for walls and window upgrade Before changing the ceilings. If the windows are still the original "Trailer" windows, upgrading to a quality double hung window alone will make a big difference.

Make sure the underbelly & skirting is tight with no holes.

Greg

[Eric_v]

Hi Greg, and thank you. Windows / doors are part of the upgrade and near as I can tell underbelly and skirting are in immaculate shape. Part of the reason for the ceiling redo, in addition to wanting to cut down on my utility costs, is two fold. One is the house is wired with 12ga aluminum wire and I'd much rather have 12ga copper so I can have all 20a circuits and the second is I'm going to be adding a theatre, cans lighting (with florescent bulbs), a return air duct to each room, etc.

But the skirting with holes leads me to a question. The skirting appears to have 'vent' holes towards the bottom 1/4 of each panel. Is that o.k or should the panels be solid? And to stay on topic, would lowering the ceiling help much?

[Greg]

You do want ventilation during the warm months under the home, but during the cold I like to seal it right up. make sure the vents are small enough to keep critters out. I have steel skirting and during the summer I remove an access panel on each side and install a screen panel.

I would question if dropping the ceiling would be cost effective. Your height and R value along the outer walls will still be the same, so you would have little gain there. You may want to see if you can get a look through the gable ends and see if there is room for more insulation already. Don't forget about ventilation up there also.

Greg

[JD]

I agree with Greg. adding additional insulation in the small void ion the upper half of the peak will not have much effect. Air flows like water and warm air will go to the area of least resistance. Since there is only 1 1/2" to 3 1/2" gap for insulation at the wall/ceiling joint on older mobile homes, they are already maxed out there with insulation. While additional insulation might slow down the escape of warm air, just like a low spot in a levy, the air will continue to flow through the less insulated areas.

The newer homes I have worked on have 10" open design trusses, allowing for that full 10" to be used for insulation space in the ceiling next to the wall.

[Eric_v]

I think you guys are missing what I'm asking. The current ceiling is vaulted with the peak at around 12 1/2'. What I'm proposing to do is remove the ceiling and lower it to a flat 7' 8" (current height of walls). That would give me a good 5+ feet from rook peak to ceiling which obviously would taper down with slope of roof.

Also, no additional insulation is being added since the old will be replaced if it's sub-par material. So new ceiling / new insulation.

[JD]

>>"5+ feet from rook peak to ceiling which obviously would taper down with slope of roof."

This is the part that I am talking about. When insulation is installed or blown into an attic, regardless how thick it is, it is applied at a consistent depth in all areas. No extra in certain areas. That is because the insulation is only as efficient as it is in the thinnest spots. So have additional space in the ridge area does not help in the insulation amount. It is good for venting control though. In the older homes with furring strip trusses, there is only a couple of inches of space right where the ceilng meets the wall. After about a foot from the edge, you could have ~ 4 1/2", which will hold up to R15 fiberglass batt. But you will still have less insulation in that last 12" to the wall, which will be the areas that air will want to pass through. Over insulating the middle could actually create a moisture problem at that edge as warm air and household moisture will pass only in this area.

And insulated roof would be a good way to go, but you are talking big bucks there. If you need a roof, this is OK, because you get a higher quality roof and insulation at the same time.

JMO

[Eric_v]

I see where your comming from JD. But what if there is no soffit or means for air to get into that last 12" of wall? Or would the air your talking about be more like convection air?

[JD]

Yes, your net R value benefit does not get better than that last 12" and doubling insulation in the middle could cause damage.

But this not saying that your plan will not be more efficient than than your current roof. I am no expert at this but it seems to me than insulation just above the ceiling and venting hot air between the insulation and roof would be more efficient. But that is just the way I see it. I have no real education on the subject. I just know that vapor barriers goes on the winter-warm side of walls and ceilings and keep your insulation consistent.

As far as if this would turn out as a savings would depend on your investment and length of time in the home. Seems like an expensive remodel to me. If you were paying a contractor to do this work, a good insulated roof might be the better choice.

[JD]

I didn't answer your question directly. Soffits is not the only issue. What I am talking about is warm air passing through roof, insulation, vapor barrier, ceiling panel and paint. Comes in in the summer and escapes out in the winter. It is the winter loss that carries moisture with it.