HVAC not quite reaching the loft/attic floor of my apartment in an old home

Question

Hoping someone might have a solution for this problem. I've got an HVAC guy coming in a few days, but it's always good to have some other opinions, and to have some people who can help me come up with some questions I can ask the guy when he comes out :)

I've just moved into the upper floors of an older home. The "main" floor of my apartment (technically the 2nd floor) is mostly open concept, save for the bathroom and bedroom. There's a staircase to the loft area that's also open (no doors), but is small (low, vaulted ceiling, have to duck or lean to the side while climbing the stairs).

At some point, my landlord had redone the majority of the inside of the house, opening things up, etc. I BELIEVE she also added HVAC at this point, though there IS an old iron vent or two in the floor on the main floor, so I'm not sure what those would've been used for. She did, however, run a vent duct up to the loft area.

The problem:

It doesn't seem to be doing much, as there's not as much cold air coming out of it as some of the other vents, and the room is still unusably hot (27-30C / 81-86F).

From crawling through the crawlspace, I can see that the vent up there uses flexible (and insulated) ductwork, goes to where the roof meets the floor of the attic at the back of the house, then travels down the wall of the main floor and connects with the vent in the bathroom. This bathroom vent provides adequate cooling though - it's just not reaching the top floor.

I'm fortunate enough that the landlord is extremely great and understanding regarding this issue, and for previous tenants, she had bought a portable air conditioner for that loft area. UNfortunately, the unit is very very loud (Too annoying to keep in what I want to be either a bedroom or office, especially with the echoey nature of the room), needs to be vented through a window (meaning running a vent tube up the only usable wall in the space), and just generally doesn't work that well. All 3 of these make using it pretty pointless.

She's open to suggestions, and seems willing to put some money into fixing it, though I'm not sure how much. Here's the space:

Wherein grey floors and yellow walls represent the space I'm cooling, blue floors represent the crawlspace, and the red line represents the duct tube / vent in the bathroom on the main floor. The darker yellow wall is the one the vent is connected to in the loft.

Here's a photo of the space / vent in question, and of the outside:

What are my options here?

• Possibly some sort of duct booster / fan to help draw up some of the air that's reaching the bathroom?
• Possibly adding a return vent? I'm not sure how complicated that is, but having access to the crawlspace might make it easier. But come to think of it, I don't remember seeing any return vents (as I know them, at least)... is a return-less HVAC system something that exists?
• Adding a ceiling fan. Though I'm not sure if there's enough head room to do that, nor is there wiring for a ceiling light. Though maybe that could be installed? Thoughts?
• Getting a split A/C system. Though there'd still be the problem with noise, and there's no good place to install the outside portion.
• Is there an A/C system I could keep in the crawlspace (reduced noise) that would be able to vent air through the roof with one hose, and vent cold air into the room through the existing hole with another?

I'm not sure what else. Any suggestions? You can see in the photos of the back of the house, there are some pipes / vents in the roof, but I can't seem to figure out what they're connected to.

Answer 1

You're asking a lot of questions here, but I think the core ones are why is the current system unable to keep the loft cool and what can we do about it?

Why is the current system unable to keep the loft cool?

The loft is getting hotter faster than your central air is cooling it. Because the loft is at the top of the house, heat rises to it from your lower floors. It also has a lot of exterior wall and roof surface, so it's being heated up faster than other areas. Cool air from the loft is able to rapidly flow down your open stairwell. Your thermostat and most of your air vents are downstairs, so your system runs until that area is cool but leaves your loft too warm.

For all these reasons, it's best to design a cooling system with the returns positioned at the top of the conditioned space. A well-designed system for your home would have a return near the ceiling of the loft. The return and any supply vents would need to be properly sized to the required cooling load. This could be done as its own zone, with a dedicated thermostat in the loft, or by properly balancing a single system such that cool air is distributed in a way that matches where your home is getting hotter, maintaining an even temperature.

What can we do about it?

You have a number of options, from full system replacement to minor improvements around your portable AC.

• You could redesign the central air system with proper returns and supplies to the loft. Depending on how close your current system is to the ideal, you could spend between $2000 and $20,000 on this. On the lower end we'd be talking about adjusting some dampers and adding a return; on the higher end we're getting into significant rework of ducting, possibly adding zoning controls, and possibly replacing the air handler and/or condenser with something more powerful.
• Tweaks to the current system. The biggest opportunity is probably around adding a return in the loft, but you may be able to do targeted changes to various ducts to improve balance.
• If you have dampers you may be able to rebalance enough; you can also do some basic balancing by closing various vents throughout the home. Try to direct as much air upstairs; if you get to the point that the upstairs is colder than downstairs, you've won! Just undo gradually until balanced.
• Add aftermarket booster fans to direct more air upstairs. These can help a little, but reviews are mixed. The kind that are installed into your ducts are probably better than the kind that sit in your vent registers, but are of course harder to install.
• Add a ductless mini-split air conditioning system for the loft. This would be a new system with its own thermostat just for the loft. This is a fairly quick install, as only power, refrigerant, and condensate lines would need to reach the loft (no ducts). You would need to add an outdoor condenser unit. Although the indoor unit does take some space, these units are very quiet and give you a lot of control - you can turn it on only when you are using the loft, and some units even offer heating.
• Upgrade your portable AC unit. A good portable AC should do fine in your room. The better units have a two-part vent line that you'd run outside through a window, which provides intake and exhaust for outside air to cool the condenser. This air doesn't get blown into your house, nor does cool home air get pushed outside -- the AC takes air from your room, cools it, then blows it around. Some units only have a single duct and are constantly blowing some room air outside for exhaust - these are less efficient. (Note that the two ducts are sometimes bundled as one hose - but you want a system where there are two separate streams.)
• Reduce heat gain upstairs. Insulation and air sealing can make a big difference, but so can simple things like curtains and window films (if you're getting a lot of sun).

Based on what you've said, I'd probably start with trying to close off the bathroom vent from which your loft vent runs. Then try closing some other supply vents to direct more air upstairs. Getting a HVAC expert to take a first-hand look should also be helpful, and I'd suggest getting a few opinions/quotes because there are likely many ways to address this.

Good luck!

Answer 2

A duct fan will increase your cooling but the duct is quite small for that area or it appears small in the photo. If the room is sealed off from the rest of the house this would further restrict air flow into the room so there needs to be some kind of opening to allow air flow to return. A small split system may be the best option. These are not large and may be the best option to condition multiple rooms, office/bedroom. The large vents on the roof are to allow the attic space to vent, some have dampers so they can be closed in the winter. Make sure these are open this alone could reduce the heat load by 5+ degrees or the possibility of installing solar powered vents. Solar powered vents have cooled several homes I have owned by more than 10 degrees this is one of my first things to reduce power consumption of AC needs.