Insulate Attic in House Hack?

[Art Maydan]

The duplex I’m house hacking has an uninsulated attic. It would cost me about $800 to do it myself. And the attic studs are non-standard distances apart, so I’m not even sure I could do it properly myself. I’m going to live here for another 1-2 years tops and will rent the whole thing out when we move on. I’m wondering if it’s worth my time and money to do if the tenant pays utilities. About how much money over the course of 1-2 winters will attic insulation save? I just got my first gas bill and it was for $120.

The only long-term argument I see is less ware and tear on the furnace. I already sealed up all of the cracks with that spray foam stuff. Are there more cheap options I’m missing?

What would you do?

[Alex Sloan]

@Art Maydan, I second the recommendation for blown-in (cellulose or fiberglass). Batts can be cheap, but almost impossible to install for optimal effectiveness. Also, if you're looking to make efficiency improvements, starting in the attic is always the best path due to the stack effect (hot air rises). Here are some tips if you will be self-installing: 

• Do as much air sealing (gun foam, caulk) as possible. Be sure to hit all major plumbing penetrations and all top plates (the part in the attic where the framing material from the walls meets the attic air plane). Insulating without a thorough air seal will render your insulation pretty useless over time, as air washing diminishes its R-value (resistance to heat transfer). Insulation does not stop air movement, so you could spend $800 on a bunch of nice new insulation, but may still witness draftiness and high utility bills if you do not fully air seal. 
• Create proper barriers for ALL heat producing devices. This can include anything from water heater vent pipes to canned lights that are not IC-rated. Here's a checklist that might help.  You'll find plenty of horror stories online about homes that went up in flames due to the insulation company not doing due diligence in creating barriers around HPDs. 
• Don't forget about the attic hatch! I recommend using a piece or two of polyisocyanurate and secure it to the hatch. You can also use a batt, but make sure it's secured nicely so that when the next guy goes into the attic, it stays on. 
• Install baffles (strong cardboard can work) for all eve vents so that your insulation doesn't get air-washed from outside. 
• If you have ducts in your attic, make sure they are well sealed before installing attic insulation. If not, you may have insulation debris distributed throughout your home, which is bad for indoor air quality. Not to mention, unsealed ducts are a terrific way to improve the efficiency of your home. 
• If your home has kneewalls, be sure to insulate those as well (basically, anything that separates conditioned from unconditioned space should be insulated)
• It sounds like you would like a platform for storing goods. Be sure to still install insulation below the platform. Dense packing with cellulose is one option. Installing polyisocyanurate/rigid foam is another. 

Some other benefits for installing attic insulation: 

• Even if you will not get the payback on your utility bills while living at the residence, it is something that can be advertised to your future tenants - "we have freshly installed attic insulation which has lowered our gas bill by 25%." 
• Improved indoor air quality: by doing a good job of sealing the attic, you are reducing transfer of air from all the bad stuff in the attic (dust, rodent droppings, etc.). 
• Reduced home maintenance: Rising hot air in an uninsulated attic can lead to snow melt and then to ice dam buildup. Proper air sealing & insulation can help prevent this.  
• Sound: insulation has a noise-reducing effect as well! Since this is a duplex, it may have unintended noise reduction qualities that will make for happier tenants.