HVAC for new room addition questions...

[ndemge]

Any guidence would be most appreciated.......

We are turning the garage into 2 bedrooms, and then turning our deck into a sunroom........

Current house is 860sqft with basement
Adding 240sq ft of Garage as 2 rooms South with Shade
adding 240 sq ft Deck into 1 room, West, no Shade


I'm going to guess that the current system will not be big enough and will ahve to be upgraded, but I need to run the ductwork now before we close up the floor.
2.5ton AC unit ..don't know about the heat.

I will be gowing from the basement directly into the floor space of the garage, where I will deck it up to be the same height as the rest of the house.

I'd like to be able to run in 1 Vent/ Retun duct and split into each room...

What size do they need to be? I'm hoping to run felxible insulated duct.

Can I do like the rest of the house and use a stud space as the return in each room?

Trying to do as much on my own without calling in a pro. If heat/air system needs to be upgraded, I won't be doing that myself.

 

[rickdb1boat]

Re: HVAC for new room addition questions...

As long as it's no more than 15' from the trunk line, run 6" flex to both rooms and use a 4" X 10" boot and grill for the supplys. In the wall return will work. Cross 3 studs to get a total of 30" for the return. A 30" X 6" return grill will work (Each Room)...3 1/2 ton unit will get the job done, but I would put in a 4 ton with no shade and facing west....100,000 BTU on the furnace.... What size ductwork do you have in the basement now and how many other supplies to rooms are there?

 

[ndemge]

Re: HVAC for new room addition questions...

I'll take some measurements and get back to you on what's there.

Sounds like a need to upgrade the system.
Furnace and air handler are 28 years old, AC condensor is only 5 years old. Are the new electric furnaces any more effiecient?
---Wouldn't see where resistive heat could be made any more efficient.

 

[BoatBuoy]

Re: HVAC for new room addition questions...

You need to get someone that's intimate w/ASHRAE standards to run loads on that space so you'll know exactly what you need. You can gestimate and get close, or maybe not.

 

[NW Redneck]

Re: HVAC for new room addition questions...

Any guidence would be most appreciated.......

We are turning the garage into 2 bedrooms, and then turning our deck into a sunroom........

Current house is 860sqft with basement
Adding 240sq ft of Garage as 2 rooms South with Shade
adding 240 sq ft Deck into 1 room, West, no Shade


I'm going to guess that the current system will not be big enough and will ahve to be upgraded, but I need to run the ductwork now before we close up the floor.
2.5ton AC unit ..don't know about the heat.

I will be gowing from the basement directly into the floor space of the garage, where I will deck it up to be the same height as the rest of the house.

I'd like to be able to run in 1 Vent/ Retun duct and split into each room...

What size do they need to be? I'm hoping to run felxible insulated duct.

Can I do like the rest of the house and use a stud space as the return in each room?

Trying to do as much on my own without calling in a pro. If heat/air system needs to be upgraded, I won't be doing that myself.

I hate to burst your bubble on the DIY approach, but you need to get a pro. That is if you want to be comfortable and have an efficient system. This is a major change to the size of the house and a proper heat load/heat loss calculation (manual J) needs to be done to determine the size of the equipment needed. Then the ducting needs to be calculated (manual D) to ensure proper air flow for both comfort and for the longevity/efficiency of the system.

If you try to 'cobble together' a section at a time you will never be happy with the results. If you install any ductwork in areas that will be inaccesable once construction is complete, then find out your 'guesstimate' was wrong, you will be SOL. Also, I would highly recomend staying away from flex in any concealed locations and use metal. Not prone to rodents or collapsing over time, and gives better air flow.

An HVAC duct system looks simple (and basicly is) but it MUST be designed and installed properly or you will have no end of grief. Problems from lack of comfort in the living spaces, to serious equipment damage are the result of poor design.

As to equipment selection/sizing:
"240 sq ft Deck into 1 room, West, no Shade" is nowhere near enough info. You need to know: outdoor summer design temp, indoor summer design temp, outdoor winter design temp, indoor winter design temp, humidity levels,building orientation, air tightness of structure, ventilation requirements (bath fans, range hoods, etc), replacement air required, # and type of windows, wall thickness and insulation value, attic insulation and ventilation, expected occupancy (# of bodies and how often). All this and more needs to be considered.

I'm not trying to offend you, but as an HVAC installer/tech I all too often see home owners spending huge ammounts of time and $$$ deciding on fixtures and finishes that can easily be changed, yet caring little about the system that will be keeping them warm/cool for the next 15-20 years that is impossible to change once construction is done. That is until they find they aren't comfortable in their gorgeous but too hot/too cool/too humid/too drafty/too noisy new home.


Again, no offense intended. I just hate seeing people unhappy in their own homes because they wanted to save money for a bigger bathtub or nicer countertops.

 

[ndemge]

Re: HVAC for new room addition questions...

NW Redneck....

The reason I ask the questions is because I want answers.
Thanks for the answers. There is no offence taken, that's why I ask.

I'm going to pay someone come out and do as you suggest, and calculate out the entire project. I'll do what I can for the new construction ductwork, but pay the pro to engineer it and install the new system.

Hey Rick, want some free steak/beer?

 

[NW Redneck]

Re: HVAC for new room addition questions...

No prob. You will be much happier with the results this way. You may be able to find an outfit that will supply the materials and you do some of the install work once it is designed. Make sure you find an outfit that WILL do a manual J&D calculation, not just using a 'rule of thumb'.

Expect to pay for the time involved in gathering the information and doing the calculations and let them know up front that you want the results of those calcs. Some outfits will not do the calcs unless they are going to do the whole job, so you may have to look around to find a contractor that will work with you. It might help to let them know you will be buying the equipment they spec from them and having them install it. Not taking the specs and looking for the lowest bid. Maybe puting a deposit down once equip is selected.

The installation of the equipment is WAY more important than the brand. Think of it like this: Say that all new cars came as a box of parts. You choose the dealer who is going to assemble it for you. Would you trust your safety to a dealer who bids lower than everyone else?

Even a Rolls Royce will be junk if it's assembled by monkeys! Good luck with your project!

 

[Mark42]

Re: HVAC for new room addition questions...

My advice is to insulate, insulate and insulate! Just insulate the heck out if it. The addition is not so big that the cost of extensive insulation will be significant.

If possable, add 2x2 furring strips to the garage exterior wall 2x4's to make them 2x6 (assuming they are not currently sheetrocked). That way they can hold higher R value fiberglass batts. Don't forget to do the ceiling too. Also good attic ventilation is needed.

These overlooked and not-too-expensive parts of additions will result in significant energy savings. Depending on how well and how extensive the insulation job, you may get away with a smaller BTU air conditioner system than you might think.

Also, call your electric company and ask for help with planning on electric service upgrade and energy saving tips. My electric company gave me specifications on what size to make the hot water base board heating elements in each room, and how many btu AC system will be needed based on room dimensions, insulation values, number and size and type of windows, and orientention (north, south, etc). This was a free service. Can't hurt to ask.

Good luck and enjoy the extra living space!

Mark

 

[Straightup]

Re: HVAC for new room addition questions...

My house was 864 sq feet before I added a 840 sq foot addition in 2000. My same furnace handles the whole house. I think it is a 90,000 BTU, but I'd have to check. I had no central air before, but had it installed. I think they put in 2.5 ton. (I'm in WI) I did most of the addition myself, but I had a local company do the HVAC. Captain is right on the insulation as my addition stays cooler in summer and warmer in winter than the old part of the house. One of the main things to do to compliment insulation, is to make sure everything is sealed up with a good vapor barrier and good windows. Then you will have a comfy space. Jeff

 

[ndemge]

Re: HVAC for new room addition questions...

First bid came back at about $2500, keep existing furnace/ac.
The room over the deck will be a logistical nightmare along with uneaven tempratures... so gonig with a seperate unit for that room.

NWRedneck...

The current supply will be undersized with the new room, lots of changes to be made over the entire system to keep it all balanced.

I'll cut the holes into the garage space and let them do the rest.

 

[NW Redneck]

Re: HVAC for new room addition questions...

You'll be glad you put a little $$/effort in now when you are nice and comfy in your finished house. Good luck with the project!8)