Roof insulation

[DanM]

Hello! I’m in a bit of quandary here in regards to how best to approach insulating the roof of my 1842 brick home.

Simply put, we have a third story that we don’t use. We don’t use it because it is in a state of disrepair. It has been on the project list for years and my wife and I have decided to get serious about it this year. I have plans to renovate it, not as a living space but as a clean and comfortable area for storage and space for my wife’s various crafts. The current roof system is as follows: typical a frame, rafters, purlins, original cedar shakes nailed directly to purlins, standing seam metal roof applied directly over original cedar shakes. No roof insulation. I’m not sure when the metal roof was installed, but I have to assume it’s old. No ridge vent, no soffit vents, no roof box vents, no gable vents, no venting whatsoever. How can I insulate this? I’ve read plenty of things online regarding this issue, I’ve spoke with my local building inspector, a residential architect, and the cedar shake bureau technical rep. The idea of not installing vents and applying closed cell foam to the underside of the original singles (possibly with a contact barrier in between) is debated. Some say you can, others say you can’t. My options are to explore this route (waiting to hear back from a reputable insulation contractor) or to have a ridge/soffit system installed and use fiberglass batts. Historic preservation is very important to me. I would rather not use spray foam if I can find another option. The toxicity of it, the permanence of it, and the idea of spray foam against 180 year old rafters makes me cringe.

That comes to my second quandary. Current code in my area (NJ climate 4a) states roofs must be insulated to R-49. This can be achieved with fiberglass batts at 14” thick. As far as I know, my 180 year old roof rafters are 4-6” thick. There’s no way that could work. And I seriously do not want to extend my rafters by 10 inches – it would have a huge spacial and visual impact on the third story (sloped walls/knee walls and chimneys coming through). Even with closed cell foam, using the max allowable thickness of 4-5 inches (I believe) I would fall quite short. I’m looking at the NJ rehab sub code which I believe states an exception in my case – stating that if recommended R value cannot be achieved due to space constraints, fill the available cavities. Which I interpret as put as much insulation as you can in there. But, unfortunately the inspector may interpret it differently and state I “could” achieve this by undertaking more construction and increasing the depth of my rafter bays. I don’t care about meeting code requirements and hopefully the renovation sub code will excuse me from doing so. Furthermore, historic preservation and using traditional, or at least more natural products (mineral wool, havelock wool) is more important to me than energy efficiency. I like my old drafty house and noisy radiators just fine.

Any thoughts at all would be welcome!

[Megs]

To start with, are those rafters (180 years old) are still good or they would need to be replaced ?

[DanM]

Well I haven’t truly inspected them. I’ll have a better look once some of the plaster is taken down. I hope they don’t have to be replaced. They’re 24” OC which obviously not the standard nowadays.

[DanM]

Rafters appear to be in good condition - dry, no sagging, and the ridge appears straight and even. Furthermore, I have no desire to replace them or anything that isn’t necessary. The rafters are 24” OC.

[WilliamFarrell]

When you find yourself facing a serious problem with your roof, you will need to call on a local, reliable roofing company near you. At House Roofing, we are committed to providing you with the highest quality repairs in a rapid manner throughout our service. We know that you may be concerned about the amount of damage you are dealing with me and we are here to help you throughout the repair process.

[ceviga]

Hello! I’m in a bit of quandary here in regards to how best to approach insulating the roof of my 1842 brick home.

Simply put, we have a third story that we don’t use. We don’t use it because it is in a state of disrepair. It has been on the project list for years and my wife and I have decided to get serious about it this year. I have plans to renovate it, not as a living space but as a clean and comfortable area for storage and space for my wife’s various crafts. The current roof system is as follows: typical a frame, rafters, purlins, original cedar shakes nailed directly to purlins, standing seam metal roof applied directly over original cedar shakes. No roof insulation. I’m not sure when the metal roof was installed, but I have to assume it’s old. No ridge vent, no soffit vents, no roof box vents, no gable vents, no venting whatsoever. How can I insulate this? I’ve read plenty of things online regarding this issue, I’ve spoke with my local building inspector, a residential architect, and the cedar shake bureau technical rep. The idea of not installing vents and applying closed cell foam to the underside of the original singles (possibly with a contact barrier in between) is debated. Some say you can, others say you can’t. My options are to explore this route (waiting to hear back from a reputable insulation contractor) or to have a ridge/soffit system installed and use fiberglass batts. Historic preservation is very important to me. I would rather not use spray foam if I can find another option. The toxicity of it, the permanence of it, and the idea of spray foam against 180 year old rafters makes me cringe.
roof replacement falls church
That comes to my second quandary. Current code in my area (NJ climate 4a) states roofs must be insulated to R-49. This can be achieved with fiberglass batts at 14” thick. As far as I know, my 180 year old roof rafters are 4-6” thick. There’s no way that could work. And I seriously do not want to extend my rafters by 10 inches – it would have a huge spacial and visual impact on the third story (sloped walls/knee walls and chimneys coming through). Even with closed cell foam, using the max allowable thickness of 4-5 inches (I believe) I would fall quite short. I’m looking at the NJ rehab sub code which I believe states an exception in my case – stating that if recommended R value cannot be achieved due to space constraints, fill the available cavities. Which I interpret as put as much insulation as you can in there. But, unfortunately the inspector may interpret it differently and state I “could” achieve this by undertaking more construction and increasing the depth of my rafter bays. I don’t care about meeting code requirements and hopefully the renovation sub code will excuse me from doing so. Furthermore, historic preservation and using traditional, or at least more natural products (mineral wool, havelock wool) is more important to me than energy efficiency. I like my old drafty house and noisy radiators just fine.

Any thoughts at all would be welcome!

Insulating an old roof can be a challenging task, particularly if you want to maintain the historic integrity of the building. There are a few options to consider that can help to balance your desire for energy efficiency with your commitment to preserving the building's character. Firstly, you may want to consider using a combination of insulation materials. For example, you could install fiberglass batts in the ceiling joists, and then use a layer of rigid foam insulation on top of the existing roof deck. This can help to provide additional insulation without requiring significant changes to the roof structure. You could also consider using blown-in insulation, such as cellulose, which can be installed in the cavities between the rafters without the need for additional framing. Another option to consider is insulating the roof from the outside. This involves removing the existing roof covering and installing insulation between the rafters. This approach can help to maintain the original roof height while still providing the necessary insulation. However, it can be more expensive and may require additional work to maintain the historic character of the building. When it comes to insulation materials, there are a range of options available. Mineral wool and Havelock wool are both good choices for those looking for more natural products, and they can provide excellent insulation properties. Cellulose insulation is also a good choice for those who want to avoid synthetic materials. Ultimately, the best approach will depend on the specific requirements of your building, as well as your personal preferences and budget. It is important to consult with a reputable insulation contractor who has experience working with historic buildings to determine the best insulation strategy for your situation. They can also help you navigate the local building codes and regulations to ensure your renovation project meets all necessary requirements.