# Insulating an old house



## jdt19942012 (Aug 2, 2017)

I am currently Renovating an old house. Gutted the entire place and am updating most everything. I took out a few things here and there on the exterior walls (a shower was against one wall, a door, etc...). I just had all my rough ins pass, electrical and duct work myself, contractor for framing and plumbing, but now I am moving onto the next stage and that's insulating. I am a little confused for the exterior walls, I understand it calls for 13+5 with the 5 being continuous insulation. But being that siding is already on one wall and I am only doing a couple patches of insulation, do I need to do the +5? Can I get by with R13 or R15 or do I really have to ripoff the siding and hang continuous?


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## mtlogcabin (Aug 2, 2017)

Fill the cavity with the maximum insulation value for the size of the cavity. 

R101.4.3 Additions, alterations, renovations or repairs.
Additions, alterations, renovations or repairs to an existing building, building system or portion thereof shall conform to the provisions of this code as they relate to new construction without requiring the unaltered portion(s) of the existing building or building system to comply with this code. Additions, alterations, renovations or repairs shall not create an unsafe or hazardous condition or overload existing building systems. An addition shall be deemed to comply with this code if the addition alone complies or if the existing building and addition comply with this code as a single building.

Exception: The following need not comply provided the energy use of the building is not increased:

1.    Storm windows installed over existing fenestration.

2.    Glass only replacements in an existing sash and frame.

3.    Existing ceiling, wall or floor cavities exposed during construction provided that these cavities are filled with insulation.

4.    Construction where the existing roof, wall or floor cavity is not exposed.

5.    Reroofing for roofs where neither the sheathing nor the insulation is exposed. Roofs without insulation in the cavity and where the sheathing or insulation is exposed during reroofing shall be insulated either above or below the sheathing.

6.    Replacement of existing doors that separate conditioned space from the exterior shall not require the installation of a vestibule or revolving door, provided, however, that an existing vestibule that separates a conditioned space from the exterior shall not be removed,

7.    Alterations that replace less than 50 percent of the luminaires in a space, provided that such alterations do not increase the installed interior lighting power.

8.    Alterations that replace only the bulb and ballast within the existing luminaires in a space provided that the alteration does not increase the installed interior lighting power.


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## jdt19942012 (Aug 2, 2017)

Thanks mtlogcabin,
so just slap in some r15 and it should pass? 2x4 wall with r15 that is.


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## mark handler (Aug 2, 2017)

Continuous insulation is the wave of the future,  If you build a wood-stud wall framed at 16 inches on center, you end up with 25-30 percent of that wall being wood, not insulation. That wood acts as a conductor which channels the heat out. or into,  the building. This can reduce your insulative value by 15-20 percent.
If you are not going to use the Continuous insulation you need to redo the energy calculations.


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## cda (Aug 2, 2017)

Welcome

Not into insulation

Not sure if the spray insulation helps your situation


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## mark handler (Aug 2, 2017)

cda said:


> Not sure if the spray insulation helps your situation


The wood still acts as a conductor


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## ADAguy (Aug 2, 2017)

Excellent exhibit MH!


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## jdt19942012 (Aug 2, 2017)

mark handler said:


> The wood still acts as a conductor



yes the wood still acts as a conductor but since there is already siding on part of the house do I have to rip it off and start over or do I just insulate the cavity and call it a day?


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## steveray (Aug 2, 2017)

Check with your Building Inspector, but MT has the right section for remodeling....


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## jdt19942012 (Aug 2, 2017)

Thanks everyone.


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## mark handler (Aug 2, 2017)

jdt19942012 said:


> yes the wood still acts as a conductor but since there is already siding on part of the house do I have to rip it off and start over or do I just insulate the cavity and call it a day?


You need to redo the energy Calculations to remove the "+5" continuous insulation.


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## steveray (Aug 2, 2017)

jdt19942012 said:


> Thanks mtlogcabin,
> so just slap in some r15 and it should pass? 2x4 wall with r15 that is.



R11 or 13 or less could work as the MT section just says "filled with insul" and doesn't give a value per inch or anything....But like I said, check with your AHJ.


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## ICE (Aug 2, 2017)

jdt19942012 said:


> yes the wood still acts as a conductor but since there is already siding on part of the house do I have to rip it off and start over or do I just insulate the cavity and call it a day?


R-13 in the stud bays that are open......take your chances with the inspector......but wait a minute here, I just checked and you are in Maryland.......insulation might matter to Maryland inspectors......here in Merryland it's not such a big deal.


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## ADAguy (Aug 7, 2017)

Not a big Deal!? No energy codes in Maryland?


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## JBI (Aug 8, 2017)

Chapter 11 of the International Residential Code (Energy provisions for one and two-family dwellings) has sections specific to alterations. Not sure what year edition is currently in effect in Maryland, but the 2015 IRC has provisions. Generally adding the continuous R-5 won't be required, but if desired it could be applied on the interior in some climate zones. As suggested above, talk to the local Authority Having Jurisdiction for a definitive answer.


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## mark handler (Aug 8, 2017)

ADAguy said:


> Not a big Deal!? No energy codes in Maryland?


https://www.energycodes.gov/adoption/states/maryland


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