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Chimney Caps / VacuStack - TDW
Please choose one of products below...

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  Vacu Stack Chimney Cap
Wind Resistant / Anti Downdraft Cap
for double and triple wall air cooled flue pipe

Above are options to fit the 3 most common metal flue pipes.
  Please call us to order any other size.

Combo priced options include and ship with...
VacuStack for air cooled flue system and factory installed 1/2" spark arrestor mesh.

The Vacu-Stack Chimney Cap solves the two wind related chimney problems -- wind induced downdraft and dynamic wind loading. The streamline flow of the wind around the Vacu-Stack prevents wind from blowing into the chimney -- even when the wind is deflected downward. The Vacu-Stack creates a venturi that causes flue gases to flow up and out of the chimney.

There are no moving parts to bind or malfunction.
Vacu-Stacks are tested by an independent testing laboratory. In the absence of wind, Vacu-Stacks provide a more than adequate passage for exhausting flue gases. The open spaces in a properly sized vacu-stack are several times larger than the flue opening. The unique design of the Vacu-Stack gives excellent protection from downdrafts caused by wind, where other devices often fail.

High quality austenitic stainless steel, T-304, guarantees superior durability for long service life. All fasteners and hardware are also made of stainless steel for complete corrosion protection. Ribbed construction provides extra strength and reinforcement. Exposed edges are hemmed for ease of installation. The Vacu-Stack chimney cap is made in the USA.

Sizing for a VacuStack

Air cooled double and triple wall flue systems need to be measured by their INSIDE measurement.

Typically... the inner pipe will be a "full" inch measurement...
IE... 8" not 7 3/4" or 10" not 10 1/4"
... the larger outer pipe will vary in size depending on the air space between the pipes and manufacturers design..

The inner and outer pipe need to be the same height for proper installation of a VacuStack.

Need extra help?  Measure and e-mail us a picture....

If the inner pipe is higher the outer pipe you will need to cut the pipe to the same height as the outer.
Note: look for any "extension" of pipe that can be removed to avoid cutting.
If the inner pipe is lower than the outer... a small section of pipe may need to be installed.

VSS6-TDW-S5 6 16 14
VSS8-TDW-S5 8 16 18
VSS10-TDW-S5 10 16 21

Downdrafts & Wind Loading

     Smoke flowing back into living areas rather than up and out the chimney can occur for a number of reasons. The backpuffing smoke signals that one or more factors may be affecting performance.
     Wind induced downdraft is one cause of smoke. Wind induced downdraft is the downward flow of air into a chimney. It can be caused by the deflection of wind by obstacles higher than the chimney such as neighboring tall trees, hills and buildings

Wind induced downdraft
from nearby tall trees
Wind induced downdraft
from nearby hills
Wind induced downdraft
from nearby tall buildings

Dynamic wind loading may occur in buildings when the wind causes negative air pressure. Negative air pressure and consequent tell-tale backpuffing may be particularly noticeable when a door or window is opened on a side of the building other than the windward side. To restore normal pressure in the building, make up air is apt to enter via the chimney and down into the living area. If the appliance is operating, smoke is then carried into the room.
    This can be remedied by cracking open a window on the windward side of the house and closing windows on the other sides. The windward side is the side the wind strikes. A Vacu-Stack is recommended as a partial solution to this problem as well.

Wind Loading on a multi-story building is another common cause of smoke and backpuffing. As the wind flows against the second story vertical wall, a high pressure zone develops at the chimney top. Although a Vacu-Stack is not guaranteed as solution to this problem, field reports show satisfactory results in more than 50 percent of the installations.

The occurrence of smoke and backpuffing when air is calm may be caused by a number of structural factors that relate to the heating system. The chimney may be too short or the flue opening may be too large or small for the heating appliances. Smoke may also occur if the chimney is blocked with soot, creosote or debris.

In a relatively air-tight house, negative pressure problems can be caused by appliances that exhaust the inside air, such as cooking ranges, exhaust fans, a clothes dryer vent, furnaces or other devices. Your individual chimney problem may be the result of a variety of factors. 


How Important Is The Connection Between Stove And Chimney?
The dimension and the seal of the stove pipe to the chimney also influences performance. Specifically, the pipe size, number of turns and length of the pipe can affect the draft.

Fireplace Insert Installation

Fireplace Adaptor Installation
Other Factors
Affecting Performance
The location of the home with respect to hills, high trees or adjacent buildings can cause problems with downdrafts. Sometimes starting a fire or keeping one going is difficult in an airtight house.

Top-vented Installation
An airtight seal is essential to prevent the formation of creosote which could cause chimney fires.

• Pictured here are three   installations with airtight seals.

Back To:
Vacu Stack
w/ Rain Shield & 1/2" Screen
(for single wall & insulated pipe)
Vacu Stack
w/ 1/2" Screen
(for air cooled metal pipe)
Vacu Stack
w/ Adaptor & 1/2" Screen
(for brick & clay liners)